I don't see any mention as to what errors are seen in the etanotify log (set the logging to DEBUG level within the Provisioning Manager under System->Identity Manager Setup). Problems can range from inbound pointing to a bad URL, trying to use HTTPS but not having proper certs, required attributes missing, etc. It is important to have inbound notifications working properly else you risk data loss and emptying the queue is not good since you will never sync those changes to the IM side now. You would best be served by opening a support case.