IRIS 1000002331 - Gmail Settings
Less secure apps & your Google Account
To help keep your account secure, starting May 30, 2022, Google will no longer support the use of third-party apps or devices which ask you to sign in to your Google Account using only your username and password.
Google might block Pantheon which is trying to sign in to your account from it.
In order to use Gmail for sending and receiving emails from and into Pantheon you must enable two factor authentication and an App password, for more info click Google Seetings.