When you try to set up your Lightroom email account with Google Gmail credentials, account validation fails. The failure occurs even if the user name and password combination you are providing in Lightroom is the same that you use to sign into your Gmail account.
Note: You could also receive a warning email message from Google regarding unauthorized access.
Lightroom Classic, Lightroom CC 2015 and earlier
Windows and macOS
Try the following solutions, in order. After performing each solution, relaunch Lightroom to check if the issue is resolved.
To understand why this error occurred, see the Google help document "Password incorrect" error.