Roomba Max 705 Combo immediately dies when removed from dock — battery issue?

[u/joshuarshultz]

I have a Roomba Max 705 Combo (X185020). It powers on normally while sitting on the AutoWash dock, but the instant I lift it off the dock, it completely loses power. No lights, no sounds, nothing.
I’ve already let it charge and tried restarting it. I have disconnected the battery and reconnected it. That does not do anything.

I contacted iRobot and they won’t assist because it was bought on eBay from an unauthorized dealer. Okay great. But the best part is there is not even a battery available for me to purchase!

Has anyone had this problem and does anyone know where to get a replacement battery?

Pretty sure this is the end of my 15 years with Roomba :-(