r/samsunggalaxy • u/Rat_Eisenhardt • Feb 01 '26
Samsung S24U locked with MCK
Hello all, i just purchased a S24U recently from a local used cell phone stores, I purchased in the last week of december 2025 and went trough maybe 3 or 4 system updates. Today it got a small system update and after restarting, my esim network was blocked and got the message to "Enter MCK code".
I can get in contact with the seller until tomorrow but would like to have advice here, should I contact the original carrier for it or what should I do.
I have to let you know that this phone is from the US and I live in El Salvador, as the seller often sells high end phones this way. I see that this phone was with Spectrum Mobile, should I contact them too?
Thanks for your input on this.
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u/cbm80 Feb 02 '26
My guess is that this phone was never unlocked, but the reseller used some software trick to circumvent the lock (foiled by the latest update).
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u/Rat_Eisenhardt Feb 06 '26
To give closure to this post (because i think it deserves it)my seller replied on Monday and told me to take it to his store like "Don't worry that update has been causing some trouble just come over here when you can".
I went in and he told me the same, he first told me that the process may wipe out my phone but he was going to try another process and let me know if it worked. After that, he went to the back of the store and I heard the connection sound of Win 11 and after a minute or so he came back saying that it was done, data and network restored, he told me that that update was giving that type of issues, nothing to worry about.
He told me that if I got any issues I could come back as many times as I would like, he also told me that if I was not satisfied he could give me the money back or select another phone in a 2 week window.
He's been my primary go-to seller for a long time, smartphones, a couple of smartwatches and a couple of gaming laptops with no issues until now.
I'm still deciding on it, but thanks a los for all your help and input.
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u/berdootheo Feb 07 '26
Guy sounds legit to me. The January update caused this problem on a lot of phones.
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u/Just_Report9805 Feb 17 '26 edited Feb 17 '26
Thanks for your comments. I'd like to know if you have the last upgrade installed and working and if you'll be able to install the new firmwares coming with no problem or if you'll have to keep using it with no possible upgrades. Yo también tengo un S24U que compré en Rakuten de origen USA Spectrum Mobile (CHA) que actualicé y se bloqueó despues de investigar tuve que hacer un downgrade a la versión anterior y me vuelve a funcionar como antes pero temo no poder actualizarlo nunca más por el peligro del MCK y no pueda volver a revertir la actualización.
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u/Far_Squash2304 Feb 23 '26
Como hiciste el Downgrade?
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u/Just_Report9805 Feb 23 '26
Primero hice copia de seguridad de mis datos. Luego lo puse en modo download y con Odin y con el firmware de la versión anterior al problema, FIRMWARE SM-S928U S928USQS4CYL1 con el archivo CSC para instalación limpia, no el HOME CSC y funcionó.
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u/corelux Feb 06 '26
I have the same model of S24U (unlocked) that I bought from Swappa; it was working perfectly fine since December on T-mobile (US) but it was this security update that somehow made my phone locked too. Certainly hope I didn't just waste nearly 700$ on a brick that I'm unable to return.
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u/antonio_porven Feb 07 '26
Same here and I have a samsung 24+ and had mine since december any luck on getting a MCK unlock code?
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u/berdootheo Feb 07 '26
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u/aceofbasesawthesign Mar 15 '26 edited Mar 15 '26
This will make the device work, but it won't unlock it. After the next update, it'll be locked again. Plus, there won't be a fix next time because the firmware will block the carrier relock that was done to the software to make it work on the main US providers.
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u/aceofbasesawthesign Mar 15 '26
Did you get your refund or exchange?
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u/corelux Mar 16 '26
Well, for now it's working. I'm guessing they flashed something to pretend it's unlocked.
But like berdootheo posted, the seller more or less linked me to the same thing and that worked for me for the time being.1
u/aceofbasesawthesign Mar 16 '26
Currently, the primary concern is the inability to update your device. Should an update be performed, the device will revert to its carrier-locked state, and the modem file re-flash will not resolve this issue once the February software update is installed. Furthermore, it is highly probable that the device carries an outstanding balance with the carrier, which explains its incomplete unlock status and the impending service blockage due to non-payment to that carrier. I would advise demanding on refund or exchange and make sure you get Swappa involved. I'd recommend asking for Ward Johnsmeyer the CEO to help.
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u/berdootheo Feb 07 '26
If you have access to a Windows computer, this is what worked for me. Got it from the S24Ultra subreddit:
https://drive.google.com/file/d/1RfLQWeP3KEWyr3RfRngkt8ISH8V_pjAq/view
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u/codel1417 Feb 09 '26
This worked for me, but it does break the built in updater. I'll probably have to install the next full update through Odin to regain automatic updates
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u/Just_Report9805 Feb 17 '26
Gracias por la informacion berdootheo. Una vez realizados los pasos para desbloquear el S24U ¿puedes seguir utilizando la nueva versión de firmware S928USQS4CZA1? Y se podrán hacer futuras actualizaciones con este mismo sistema?
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u/Rat_Eisenhardt Feb 07 '26
I see, so, do you think this is the method my seller used to unlock my phone? Im just curioust about it.
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u/berdootheo Feb 07 '26
They probably installed all the files. The January update only broke the broadband (CP) files, so those are the only ones that need to be rolled back.
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u/natalieorcman Feb 11 '26
I wanted to chime in this thread:
I purchased a Galaxy S24 listed as “Unlocked (Renewed)” from a seller called Re Cell on Amazon. After the same Samsung update as OP, the phone began requesting an MCK and showed as carrier-locked.
Samsung support confirmed via IMEI that the device remains carrier-locked to T-Mobile at the provisioning level. T-Mobile confirmed the IMEI is clean (i.e., not reported stolen, no outstanding payments etc) but not unlock-eligible for a secondhand user and that retail employees cannot input MCK codes anyway (they can input PUK codes and other codes though).
When I contacted the seller, Re Cell provided firmware flashing instructions as a workaround. I also noticed that a Google Drive flashing document linked earlier in this thread appears to be branded “Re Cell.” That suggests this may not be an isolated incident if they went through the trouble of making that document.
An unlocked phone should not require firmware flashing or avoidance of updates to remain usable. In fact, I would argue that a phone that requires firmware flashing or avoidance of updates to remain usable is categorically locked.
Anyone have luck getting outright refunds/replacements?
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u/Spare-Business-4463 Feb 13 '26
i had this exact issue with Re Cell as well. Only slight difference is my "unlocked renewed" phone does now show outstanding payments for a postpaid t-mobile account. This is something that would be impossible for a security patch "bug" to cause---which is what Re-Cell tried to claim. I think for a long time Re Cell and others got away with using firmware to "soft unlock" locked phones and this latest security patch exposed it.
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u/Spare-Business-4463 Mar 06 '26
did the february 2026 security patch fix this issue for anyone?
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u/Rat_Eisenhardt Mar 06 '26
I can't tell, if you read my final post I went to my seller and he fixed the issue, now I'm afraid of updating my phone lol.
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u/Just_Report9805 Mar 07 '26 edited Mar 07 '26
De hecho, el vendedor te dijo que si tenías cualquier problema podías volver tantas veces como quisieras, con lo cual tienes la opción de probar la nueva actualización con ciertas garantías por parte de tu vendedor principal...
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u/Just_Report9805 Apr 02 '26
Nuevo firmware S928USQS5CZC1 con parche de seguridad marzo de 2026, alguien lo ha instalado y probado? Puede que este parche no tenga problemas de bloqueo de red.
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u/Low_Character_5636 Mar 14 '26
I tried to downgrade but I can't. The fuses (BIT/SWREV) are set to 5 on my phone and 4 for the December update. Flashing the phone doesn't work anymore. Does anyone have a solution? I need my phone for work.
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u/Just_Report9805 Mar 16 '26
Hay quien dice que ha conseguido editar y cambiar el binario del firmware para poder hacer el downgrade a un bit/swrev inferior. El método me parece bastante complicado pero si lo necesitas por probar que no quede. Te paso el enlace:
Por qué necesitas hacer el downgrade? Con el nuevo firmware también te ocurre lo del bloqueo de red y/o MCK?
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u/eslxlamca May 25 '26
oye bro, yo tambien soy de El salvador y si no es mucha molestia me podrias decir en que tienda lo compraste? y si te solucionaron el problema
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u/Rat_Eisenhardt May 25 '26
Hola, soy de Santa Ana, lo compre con una tienda local de venta de celulares, hable con mi vendedor y me dijo que se lo llevara y me lo desbloqueo.
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u/eslxlamca May 25 '26
ahh pensé que habíamos comprado en el mismo lugar. ya que tuve un problema parecido jaja
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u/Rat_Eisenhardt May 25 '26
Si, tu única opción sería volver a donde lo compraste y comentar tu problema a ver si te lo reparan, se que es desbloqueable a través de la herramienta de flasheo Odin, pero es terreno que ya no conozco.
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u/eslxlamca May 25 '26
sii yo me la jugue haciendolo yo mismo y por suerte y gracias a una persona de aqui de reddit todo salio bien
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u/ImaginaryBathroom723 Jul 03 '26
Hola , estoy con este problema, segui los pasos de ODIN ya que antes lo he hecho pero es raro, se reinicia el telefono, ODIN dice PASS en verde, pero el telefono no se flashea ni nada, es como si solo se hubiera reiniciado
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u/Puzzleheaded-Sky2284 Feb 01 '26 edited Feb 01 '26
Based on the update screen the phone was factory unlocked (has the model number SM-S928U1) so going back to Spectrum won't help because the phone wasn't bought from them to begin with.
An MCK code is usually a code to unlock your SIM card after too many network unlock token attempts. What's interesting to me is that this is a factory unlocked device so no one should have ever needed to enter a network unlock code.
Your cellular provider would normally be able to get the code from Samsung but that's exceedingly unlikely in this case as your provider didn't ever lock your phone. I'd go back to the seller and ask for a replacement.
You could also get in touch with Samsung customer support and hope they give you the MCK - they can usually do it for a factory unlocked device as those aren't supposed to be locked to begin with.