I am, for some unknown reason losing my gmail/iCloud service on my MAC

My service is being interrupted by the little lighting bolts in shaded dots to the right of "Inbox, iCloud, and Google? This problem is only on my Mac. My iPhone works and my PC laptop works with gmail. I must reenter my password for gmail or for iCloud in an effort access my mail, but even that doesn't work now. I enter my password and it thinks for 5 seconds and I get a dialog box with nothing in it except the word cancel. Sometimes I can send but not receive and sometimes I can receive but no send; however, now I can do neither!