I went to AOL to reset my Verizon password and everything worked fine on the AOL email site. When I went to my desk top PC, I could not send or receive emails with my new password change. After thoroughly searching the net, I was not able to find an answer. If others are having this problem, this is how I fixed the problem.
Whenever I went to put in my new password in Thunderbird it was rejected. I checked the AOL email site and saw everything looked good and I was able to send and receive email. While looking through the AOL options, I tried this:
Options [Upper right corner] =>Account Info=> Account Security=> Manage App Passwords=>Select your App=>[Choose applicable App or Other]=> Thunderbird=> Generate [Important - Write down this password. You will not be able to bring it up again without generating a new one.]
Go to Thunderbird and try to receive email. If there are no emails go to the AOL site and send one to yourself. A box will come up asking for your password. Do Not use your new generated password to access email on the AOL site. Use the password you changed originally. You should now be able to receive emails.
I could receive, but could not send emails. Here is my fix. In Thunderbird click on Tools=> Account Settings. Go to bottom of left panel and select Outgoing Server (SMTP). Click on the SMTP server you are using to access Verizon/AOL and carefully write down the server information. Remove the server from your list. If you only have one server and it is the 'Default' server, you won't be able to remove it. I have two email accounts so I made the other one the 'Default' server and was able to remove the Verizon server. If you only have one email account, you might be able to make up a dummy server and then delete the Verizon server.
Close Thunderbird and open it again. Go back and try to send an email. A box should come up and ask for SMTP password. Put in the one you generated with the 'Manage your app' option. Send an email and in my situation, it worked and I am able to send and receive emails on my Verizon/AOL account.
You may also want to remove your old incoming and SMTP passwords. Go to Tools => Options =>Security =>Saved Passwords