Outlook 2011 for Mac stuck in continuous download loop and showing ‘unread’ msg that’s not there

I am using Outlook 2011 on my Mac.  I have the latest Outlook loaded on a PC as well.

On my Mac, it is stuck in a continuous loop showing an unread message and saying in the status bar that there is a sync pending then that it's downloading attachments - which never happens.

When I use Outlook on the PC, this does not happen and all messages show as read.  Logging into web access for my account shows the same as the PC - nothing unread or pending.

I did a 'cache empty' of the inbox, have re-installed Outlook and have restarted both Outlook and my Mac.  None of that has worked.

Help !  This constant cycling is causing slow performance and irregular behavior within Outlook.

Any guidance is appreciated.

Thank you.