Gmail Account Won't Register

Please clarify what you mean by "won't register", and "functions on IMAP".

There seems to be a contradiction.

If the account is not working, but "functions"...

I am sure it a matter of wording, but please clarify.

Note that gmail has completely dropped support for POP3, so indeed IMAP is your only option if you want to use it with the Apple Mail application; also, in order to "register", you should be rerouted to a web page in Safari to confirm your gmails credentials. Maybe it's that part that is not succeeding

Sign in using app passwords

An app password is a 16-digit passcode that gives a non-Google app or device permission to access your Google Account. App passwords can only be used with accounts that have 2-Step Verification turned on.

BioRich wrote:

• For some reason a gmail account simply won't register.

I've deleted it twice

It functions on • IMAP

• This account is not new. Over 15 years old. I use it daily.

• New password but functional

I am logged into Google• services. I've logged out then back in.

I've quit my Mail.app• more than once.

I'm using Apple Mail.app which also integrates with Accounts in System Preferences• .

Anybody know what I'm doing wrong? How can I fix this? Cheers

I do not know exactly what the issue is or where when you say "For some reason a gmail account simply won't register. "

If you can not set up a gmail account—verify you have Safari set as the default browser and compare your results

Make Safari your default web browser on Mac - Apple Support

you can set it back later....

Have you queried gmail support for gmail issues—

use the steps from Google

https://support.google.com/a/answer/9003945#zippy=%2Cset-up-gmail-with-mail-on-a-mac

Otherwise you are going to have to paint a bigger picture of your problem.