You didn't provide much detail, so bear with me for awhile. There are a number of possibilities.
Gmail
It may not seem intuitive. First of all, are you able to login to your alternate email, you needed one to setup Gmail? The reason I am asking this is that the first thing to check is that your password is not correct. Remember that Gmail's password is case sensitive, so double check that you have entered it correctly.
Next are you able to read/send/delete/archive your Gmail from a browser? To troubleshoot this, if you don't have the Chrome browser, get it. In the Chrome browser, at the initial screen, click on skip for now. Then go to
https://www.gmail.com. Are you able to login to Gmail? If you can login to Gmail from the Chrome browser. If your password is incorrect, and you don't remember it, you may request it to be reset and the new temporary password will be sent to your alternate email, so you'll need do access that account to read your password and the instructions to using it.
Once your password is correct, or you are able to get in to Gmail in Chrome, you'll need to confirm a couple of settings in Gmail. Click on the gear, and select
Settings. Along the top you'll see several settings, select
Forwarding and POP/IMAP. Next, ensure that POP is disabled and IMAP is enabled. If that is not the current setting, change it. Click on
Disable POP and click on
Enable IMAP. After making those changes, you MUST click on the
Save Changes button. If you miss that step, it won't change.
Mac OS X Mail App
Now everything is setup correctly in Gmail. The next is in the Mac OS X Mail app. In the Mail app, select the
Mail menu item and go to
Preferences... then select Gmail or whatever you called it. There will be three tabs shown. Select
Account Information. Then in there, make sure that your
Email Address is your fully qualified Gmail address, meaning
<user id>@gmail.com. Then, go down and make sure that the
Incoming Mail Server is set to
imap.gmail.com. Then the
Outgoing Mail Server (SMTP) is set to
Gmail.
TLS Certificate should be set to
None.
Now go to the
Advanced tab. Then make sure all the top half check boxes are checked except make that the
Send large attachments with Mail Drop not selected. Leave the
IMAP Path Prefix blank. Then make sure that
Port is set to
993 and that
Use SSL is checked. Also that
Allow insecure authentication is NOT checked. Check the
Use IDLE command if server supports it.
Now close that Accounts pane and close and restart Mail. It should already connect and be on-line, but just to be sure, restart Mail.
This should solve any setting issues. Let me know if you are able to login via the Web Gmail, via the Chrome browser but it still shows as off line in Mail. Btw, I’m available to help over the phone in case u need at
https://www.6ya.com/expert/mark_1e5d703456353ef9