Is there mail arriving when you check the account through webmail? There may be a corrupted message that is blocking download through TB. Delete messages, via webmail, from around the time the problem started, until normal access via TB resumes.

https://support.mozilla.org/en-US/questions/1158670

forgive me but I can not delete the messages, there is no other solution ?

Can you not access the account through webmail? Who is the mail provider?

via webmail everything works

it's really strange it's like if thunderbird has decided to stop

Yes, so you have to delete the message(s) that is stopping the newer messages from downloading to TB. Look for the ones that arrived just before the problem began. Once it, or they, are removed, the newest messages should download to TB.

it would be like looking for a needle in a barn

Look at the Date for the most recent message that arrived in TB, then look at the message that arrived in webmail just after that Date. If deleting that one doesn't help, delete the next newest one until downloading resumes. Or, move a bunch of messages to a subfolder of the Inbox.

Thanks for the answers, I think this solution for the last one waiting for others ...

I am not sure what you mean by accessing the account through web mail. I searched the web on how to do this but was unable to find a satisfactory answer. As a last resort I deleted the account and then reinstalled it again. This corrected the problem and restored both old and new emails. I'm not really sure why this worked, or what happened in the first place.

DavidW631 said

I am not sure what you mean by accessing the account through web mail. I searched the web on how to do this but was unable to find a satisfactory answer. As a last resort I deleted the account and then reinstalled it again. This corrected the problem and restored both old and new emails. I'm not really sure why this worked, or what happened in the first place.

Practically every ISP and mail provider such as Gmail, outlook.com, AOL etc. lets you access an account by signing in on a webpage. Who is your account provider?

as a Internet provider we use http://www.fastweb.it/ and gmail but I open the wireless with the tools fuxion and KRACKATTACK because I am a researcher and and I am also an unemployed CCNA, I think I will not reinstall thunderbird anymore because the computer it belongs to my mother and she is not able to solve this problem I'm sorry because thunderbird is a great software but I can not solve this problem every time, thanks to all the answers

A good starting point is to look for any error messages. The second thing to do is turn off any email scanning in your anti virus program. Then log into the mail using a web browser and empty the spam folder on the providers web site. Most download issues arise from badly formed emails, the worst are usually spam, so emptying the spam folder on the providers web site often is all that is required.

Thank you the problem is solved