Had a customer who needed to change their Gmail password. When they opened Outlook it asked for the new password, so they entered it. Outlook keep prompting for the new password.
The customer could go to Gmail and log right in.
It turned out to be Google needs this account to be “Less secure apps” section of your Gmail account. It should be here https://myaccount.google.com/lesssecureapps. Turn on this feature.
Let us know if this solution helps you…