Workmail Login intermittently fails

I'm the technical resource for a group. This is happening with MY account so its something I have not seen before. At different points in the day, I go to use Thunderbird email client and it asks me to retry or re-enter a new password. I go to Workmail web site, and try and log in with the same credentials and it says they are bad credentials. I go to the Workmail admin portal, change my password there - no difference, no matter how long I'm waiting. I have used the link for the webmail provided in the portal so that there is no confusion. I still get back credentials in both Thunderbird and Webmail. If I edit the account, make a change, save it, the same credentials that failed a moment earlier now work for both webmail and Thunderbird. Other users in this domain have not reported any issues. I have deleted the account in Thunderbird and added it again, with auto configure of the server details and it works for a short time, then same problem. This one is confusing and driving me nuts.

TIA