This kind of problem
generally occurs when you have recently activated the Google Authenticator
Verification and there is also a requirement of setting up the
2-Step-Authentication in your Gmail Helpline Phone Number account.
For this, you need to visit
the link after getting this job done, you also need to go back to this page and
click the "App Password" - Settings.
Don’t forget to choose "Other
(custom name)" and enter the name of your choice. Then take a further step
and copy the code and paste it to your projects settings. Gmail Phone Number
It’s done now.