Unable to logout of iCloud on iPad Air 2

iCloud sign-in/out and Verification Failed Issues

I have an older iPad Air 2 running IOS 15.8.4 which I recently updated. Due to space issues, I needed to reset the iPad as part of the update to the latest IOS available. I performed a backup beforehand which I attempted to install after the update. It seems to go OK, but now I can no longer log into my iCloud account and receive the known 'Verification Failed' msg. I checked the credentials several times, changed the password a few times and tried the various fixes found here, but with no luck. I can log in on other devices using the same credentials.

I was going to reset the entire iPad, but cannot as I need to log into iCloud to shut off "Find My" to return to factory condition. Since it won't take my credentials and password, I am stuck.

I noticed that the Apple ID settings show that I AM logged in, but I cannot log out. The "Sign Out" button is red, not grey, but does not react to input.

If I log into my iCloud account, under devices, the iPad does not show. If I unplug the USB cable and re-insert it, it asks if the device should be trusted and I confirm yes.

I have tried all sorts of fixes listed here and on the web, but nothing has worked.

Anyone have some advice towards a fix. I am stuck.

Thanks, Mike

[Re-Titled by Moderator]