So this is a Gmail account, right? Have you set it up in Thunderbird as POP or as IMAP? Do you also access this account from some other device or application?

It is an Imap. It has been the same Gmail for years and was working up to yesterday. it is up to date and I have restarted it and the computer. It does everything like it is going to check mail but says there is not. I can see there is if I go to Gmail. I can send mail. I have been getting a security certificate pop up for a couple of weeks that I have been telling to continue anyway. I get the same one on e out going mail .

Any error messages you get would be important to diagnose the problem. You need to report that info more accurately by either providing screenshots of them, or typing here what is it exactly that they say.

this is what I was getting but do not any more when I collect mail. I still get it the first time I send mail after I open it.

I wondered about removing gmail and re attaching it. but its not collecting my blog feed either. Thanks for helping

This being an IMAP account, you may try removing the account (I'd remove both account info and message data in this case), and set it up in Thunderbird again, indeed. Everything stored on the server should be back when Thunderbird synchronises with the server after setting up the account, but make a backup copy of your profile folder first, just in case.

BUT…

The alert you're getting is weird because you would typically get that alert as a result of having misconfigured Thunderbird to use the wrong mail server, which causes Thunderbird to not be able to find the certificate it expects to find for that kind of server… but you appear to be using the right server for a Gmail account, which means you may encounter the same problem again after re-creating the account in Thunderbird with the same settings…

So you may try re-creating the account in Thunderbird, but I'd like you to post a screenshot of both your incoming and outgoing server settings first, so I may check that everything there is correct.

HI Not sure what or where the profile folder is. If I delete the email form the settings and then remove the program will it effect the email on google? her is a shot of the setting. I don't see anything that has changed.

A link to the article that explains profiles and how to find and manage them was included in my previous reply. Didn't you notice "profile folder" was a link there? I'll type the URL explicitly here for reference:

https://support.mozilla.org/kb/profiles-where-thunderbird-stores-user-data

Removing the account from Thunderbird merely deletes what Thunderbird stores locally on your computer for that account, not what's on the server.

You only posted the incoming server settings, not the outgoing ones, but they look right to me, so if you have incoming mail problems, re-creating the account in Thunderbird is what I would try next, yes.

Turn off antivirus scanning of the profile folder and scanning of secure (SSL) connections, and see if the certificate 'error' disappears.

I decide to uninstall it. I saved the most important stuff my gemail addresses in the settings leaving only old blog feeds I din't care about. I deleted it yesterday, reinstalled it today and that solved the problem. I was surprised to see all my blog feed stuff reload rather than having to start over. A nice surprise. Who know why it suddenly stopped working on Saturday. Thank you for giving me options to solve the problem.