Continue to have "Authentication Required" POPup errors at startup.

After reinstalling a Windstream.net email account I continue to have Authentication Required errors at startup. Popup messages only occurs during thunderbird startup. And Only on my Windstream.net email accounts. not my outlook.com and Gmail accounts. the following is the popup window during Thunderbird startup. "Authentication Required - Mozila Thunderbird https://imap.windstream.net is requesting your username and password." I entered the username and password and check the save box. The popup returns with the same error asking for the same info. If I just select CANCEL, it pops up 2 more times and after the third cancel, the popup shows no more. The account fills with any incoming emails from Windstream.net. The Windstream.net account seams to work normal from that point on. I Can send and receive fine with no more popups. Until I restart thunderbird then this error starts all over. Is this a thunderbird or Windstream.net issue? Any suggestions on a fix? Also I have a gmail and outlook.com account with no issues.