Gmail Temporary Errors

[JHand]

Recently many of my Gmail files produce 'Temporary Error' notices when I try to open them. Searched here with no luck. I've stripped off all extensions and add- ons, reinstalled Gmail, run trouble shooting, etc. This amounts to data loss. Help?

 

[JHand]

No and am puzzled; I've noticed many identical complaints during my searching and never any useful responses in Gmail help, Firefox help, nor in this very forum. Problem started for me about a year ago--maybe less--and I've no way to set system that far back. Can not see any pattern in when, subject, etc.