I was wondering if anyone has got OAuth 2.0 for Gmail working OK.  We have a customer where it set up and working OK after adding the Client ID and secret but then after a while, potentially just an hour you start getting errors when sending an email.  You then re-enter the same Client ID and secret and it starts working again.

this is in the logs
Apr 3 2025 10:38:16.871 10220 8972 5 doEndpointPostOAuth2KeyGen(401): {
"error": "invalid_client",
"error_description": "The OAuth client was not found."
}
Apr 3 2025 10:38:18.066 10220 8972 5 SMTP: Could not send message. This may be due to AUTH not being supported by the MTA, no supported authentication methods being available, or an incorrect username / password. Retrying using AUTH LOGIN. Message: EIdSMTPReplyError: Username and Password not accepted. For more information, go to
support.google.com/.../ 5b1f17b1804b1-43ea8d16d35sm55780915e9.0 - gsmtp

Apr 3 2025 10:38:18.405 10220 8972 5 SMTP: Cannot use AUTH LOGIN. This may be caused by authentication not being enabled on the MTA, or an incorrect username / password. Retrying without authentication. Message: EIdSMTPReplyError: Username and Password not accepted. For more information, go to
support.google.com/.../ 5b1f17b1804b1-43ea8d16d35sm55780915e9.0 - gsmtp

Strange how it just stops working, I have raised a case with support but was wondering if anyone else had the same issue.