imap authentication not working

[ajendrex]

Hi!

I have an access token with scope https://www.googleapis.com/auth/gmail.modify and which I validated with SMTP to send emails. The same token used to try oauth2.py from this repository seems to be invalid:

python oauth2.py --test_imap_authentication --access_token=<access_token> --user=<email_address>

  18:48.35 > b'ILPK1 AUTHENTICATE XOAUTH2'
  18:48.50 < b'+ '
  18:48.50 write literal size 364
  18:49.49 < b'+ eyJzdGF0dXMiOiI0MDAiLCJzY2hlbWVzIjoiQmVhcmVyIiwic2NvcGUiOiJodHRwczovL21haWwuZ29vZ2xlLmNvbS8ifQ=='
  18:49.49 write literal size 364
  18:49.64 < b'ILPK1 NO [AUTHENTICATIONFAILED] Invalid credentials (Failure)'
Traceback (most recent call last):
  File "/Users/hurbina/src/gmail-oauth2-tools/python/oauth2.py", line 353, in <module>
    main(sys.argv)
  File "/Users/hurbina/src/gmail-oauth2-tools/python/oauth2.py", line 338, in main
    TestImapAuthentication(
  File "/Users/hurbina/src/gmail-oauth2-tools/python/oauth2.py", line 282, in TestImapAuthentication
    imap_conn.authenticate('XOAUTH2', lambda x: auth_string)
  File "/Users/hurbina/opt/anaconda3/lib/python3.9/imaplib.py", line 444, in authenticate
    raise self.error(dat[-1].decode('utf-8', 'replace'))
imaplib.IMAP4.error: [AUTHENTICATIONFAILED] Invalid credentials (Failure)

I'd appreciate very much some help to understand what is wrong.

Hector.