What exactly are you doing when getting the error message?

Can you post your Troubleshooting Information? At the top right of the Thunderbird window, click the menu button , then select Help > Troubleshooting Information. Press the Copy text to clipboard button and paste the information into your reply.

What are the new server settings as per your email provider information?

sorry. not understanding what you want me to copy and paste.

the settings asked for by Hostmonster are host413.hostmonster.com for incoming with IMAP, PORT 993, SSL/TLS, normal password host413.hostmonster.com for outgoing with SMTP, PORT 465, SSL/TLS, normal password

It isn't rocket science. https://support.mozilla.org/en-US/kb/forum-response-asking-troubleshooting-information

Application Basics

   Name: Thunderbird
   Version: 38.6.0
   User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0
   Profile Folder: Show Folder

             (Local drive)
   Application Build ID: 20160211132445
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory

 Mail and News Accounts
   account2:
     INCOMING: account2, , (none) Local Folders, plain, passwordCleartext

 Crash Reports

 Extensions
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is this what you need?

Troubleshooting Information shows that there is no 'hostmonster' account at all.

Again, what exactly are you doing when getting the error message?

had to change the server hostname and ports for incoming and outgoing on Thunderbird,

Whatever you did, you somehow managed to delete the existing account. Please explain in more detail what you did.

I am replying to this email from my [email protected] account via roundcube, so I know that it is still working on the Hostmonster end. I deleted the account on Thunderbird, because I could not get the new settings from Hostmonster to work. then I uninstalled Thunderbird from my desktop after unsuccessfully trying (numerous times) to get it to work by adding a new account. Once reinstalled, I attempted to set up from scratch, but still getting same error code.

Make sure Thunderbird is not running (a reboot might make sure) in the start menu type %appdata% and press enter. Windows explorer should start showing the appdata folder (hidden) Delete the Thunderbird folder. Restart Thunderbird.

worked immediately. thank you very much, Matt.