The only other reason if you get stuck in a loop trying to authenticate a Gmail account is if you have eg: Windows 10 and have enabled TLS 1.3.
Can’t create gmail account, stuck in authentication loop - Mail - eM Client
Quote from @Gary post from the above thread.
“Have you by any chance enabled TLS 1.3 in Windows 10?
If you have, it is not compatible with that version of Windows, and so you will need to disable it again. Once that is done, try adding the account again”.