I need to know how to make the program receive emails

See https://support.mozilla.org/kb/cannot-receive-messages

Also, please post your Troubleshooting Information. At the top right of the Thunderbird window, click the menu button , then select Help > Troubleshooting Information.

There's also an issue regarding passwords.

So basically you said there's a problem, but not what the problem is.

I downloaded Thunderbird. Every email saved, and the organization of saved emails, were included, but there's no site marked "Tools" and no place with three lines on top of each other. So I wasn't able to do what the instructions advised.

My Thunderbird sends emails, using a password I got from AT&T, but hasn't received any emails since June 11. What else can I do?

So your Thunderbird has no way to write a new message or open your address book is that right?

I don't know if this will help but I had a similar problem after the 3 June '21 update. I receive my email via AT&T/Yahoo. I just posted how I solved my problem. In a nut shell it was a problem with the AT&T Secure Key - which is nothing more than a very long password. I went into my AT&T Profile and selected the Secure Key option, deleted the existing key and created a new key. Opened TB and used the new Secure Key as the password and TB started working again.