Re-authenticating Inboxes
This also means that replies and bounces will not be detected until the inbox has been re-authenticated.
How to know if an inbox lost authentication?

How to re-authenticate inboxes?
If you have access to the inbox
If you have access to the inbox, you can re-authenticate the inbox by clicking Continue with Google from the General Settings of the inbox.
If you don't have access to the inbox
If the inbox that needs to be re-authenticated is owned by another person (eg. a client inbox),
click the Get shareable link to re-authenticate.
An invite link window will pop up, click Copy link to clipboard and send the link to the inbox owner.
Once the inbox owner goes to the link, they will be asked to sign in with Google to re-authenticate the inbox.
Once the inbox has been re-authenticated, an email will be sent to the admin of the account who generated the invite link.
Once the inbox has been re-authenticated the red highlight of the inbox will disappear.
Note: Once the disconnected inbox has been re-authenticated, all pending emails will send immediately, so if the inbox has been paused for quite a while, we recommend pausing the active campaigns first.