Client upgraded from 10.2.1 to 10.3.1 for Forms. Post upgrade, submissions made indicated that they were completed but that it couldn't show a preview of the submissions.
There were no records of such submissions in Forms nor did they show up in the repository. The Client has a Forms in the DMZ as per the LF recommendation and these submissions were made to through the DMZ instance.
Restarting the Forms Routing Service on the internal forms resolved the issue.
Is there anyway Client see how many submission attempts were made during the period [about 2.5 hrs] that this issue persisted?