The error "Could not authenticate with provided details" occurs when an incorrect password is being used.
When connecting a Gmail or Google Workspace email account as a custom email, without using an App Password or if IMAP is turned off.
Learn more here:
Connect Google Workspace or Gmail
Follow the steps below to setup your G-suite email account as a custom email address:
If you’re not using Gmail, it means that your provider requires you to use an app password (most likely because you have two-factor authentication to log in to their service) or an API key as the password. Please check with your provider.