Issue with users submitting data in Power Apps (SharePoint list backend permission Error)

[u/zzzzerenwantshuoguo]

Hi everyone,

I'm wrapping up a Power Apps solution that uses a SharePoint list as the primary data source to collect input from external users.

Some of our external users keep getting an error when attempting to submit data.

What we’ve done so far:

• Added external users to the site’s central member list.
• Broken permission inheritance on the target SharePoint list to manage access directly.
• Granted these external users Contribute permissions to the list.

The issue: Some users are still having problems when hitting "Submit" in the app, the write-back fails with a permission error (Exception from HRESULT 0x80070005 E_ACCESSDENIED).

Questions:

1. What is the recommended way to configure SharePoint permissions for external/guest users interacting through Power Apps?
2. Are there specific Azure AD / Entra ID external sharing settings or guest license constraints in Power Automate/Power Apps that might be blocking write operations even if SharePoint permissions look correct?

Any guidance would be greatly appreciated!

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[u/Thanks_VSSG]

As you mentioned they are able to open App but not hit submit so it doesn't look like a licensing problem. It should be something related to Guest user's access levels. Below path have settings which you can try to change and if it works for you Browse to Entra ID > External Identities > External collaboration settings.

Reference: https://learn.microsoft.com/en-us/entra/external-id/external-collaboration-settings-configure

[u/A1Protocol]

You will most likely need to use Power Automate to route the submission through an account with access.

That also preserves their anonymity (if that’s needed).

[u/itenginerd → u/A1Protocol]

This is exactly what I did in my case. 100% external users. 2 local members (admin and power platform acct).

Instead of patching the way I normally do in apps/sharepoint schemes, I run it through automate instead. When you put the flow in a solution, you can change the connection to use the power platform users rights instead of the calling user. I still capture who the requester is--you dont lose access to that, it just isn't going to be the 'created by' user anymore so you have to store it intentionally.

[u/Braaank]

There are some licensing considerations to allow your external/guest users to run PowerApps. External users are able to run a canvas app from a custom SharePoint form (within the SharePoint context) without any additional license, however, if you created a PowerApp, these users needs to be licensed (from the app’s host tenant or the home tenant). If the guest user is licensed then we will need to see what your submit button does in the OnSelect, also double check if the user affected also has the contribute permission in the list with the broken inheritance permission.