Removing the Beta profile does not remove the installed iOS version. Your iPhone is still running on iOS 15 Beta version.
(1) Try and Force Restart your iPhone EXACTLY as shown below and see whether that resolves the issue:
- Press and quickly release Volume UP button
- Press and quickly release Volume DOWN button
- Press and Hold the SIDE button until an Apple logo appears and then release the Side button (Can take up to 20 seconds. (DO NOT release Side Button when invited to Slide Power OFF).
(2) If the above does not work then - I recommend that you wait it out till early next week when the official iOS version 15.0 will released to the general public. You have already removed the Beta profile so when the official update is available then you will be able to update to it.
Axel F.