This is probably a case of a bad password in the UI in Luminate Online.  You may notice that syncing is working normally, except for this message.  This is due to the Service Bus working properly, but the other part of the Sync requires a different password, and that has most likely been changed incorrectly.

If you know the correct password, here is what you do:
  1. Go to Data Management -> Luminate Configuration
  2. Go to Step 1. Configure Connectivity
  3. On Step 4. Enter the correct password in both fields
  4. The error should now go away once refreshed.
If you do not have the password, Contact Support and provide this article number, so an analyst can track it down.