If you haven’t done it already, please send the log file from the Cryptomator for Android app. Tap “…” at the top-right and select “Settings”. After that, you can select “Send log file” at the bottom. Maybe we can gain some more information on the error message. Thank you!
I had exactly the same issue, Cryptomator Android App crashed when trying the “back” button on the Microsoft page. App was then closed by the OS. After starting it again, I could click on “Business account” and see the folders in OneDrive for Business.
So, apparently the log in did work despite the error message.