Four possibilities I can think of:

1. You only mentioned the NetBackup version number.  OpsCenter needs to be at the same or higher than the version of NetBackup on the master server.  If you are not using OpsCenter 7.5.0.3, upgrade it to that version.
2. Make sure that Data Collection is successful.  "Settings" -> "Configuration" -> "NetBackup", at the bottom of the screen select "Data Collection Status" tab and make sure the "Job" collection is current. If it hasn't run in the past few minutes or so, make sure the Data Collection Properties are set correctly and/or try restarting the OpsCenter services.
3. Some of the filters can be inadvertently set wrong on the report setup screens.  For example, in a custom report, I have frequently had a report filter somehow set various filters like "Disk Pool Name" to just the very first disk pool, but I never set the disk pool filter at all. Go into your custom report's definition and select each of the filters one by one, even the Master Server filter, and make sure everything is still set correctly.
4. There is always a possibility of report definition corruption during the upgrade.  To check if that's the case, create the report from scratch again and save it to a new folder and see if that corrects the problem.  If it does, be sure to post back here.  I have an open case for some error messages appearing when I try to alter and save updated custom reports, and Symantec believes there may have been some sort of database corruption during my upgrade process.  If that's truly what happened to my system, I would not be surprised to learn that more than one OpsCenter upgrade encountered similar issues.

Thanks--I upgraded to 7.5.0.3, bust still no data in the report.  Interestingly, the data IS represented in the Opcenter OVERVIEW console, it just no longer shows up in the report that has been running for months.  As I mentioned, I can't seem to find the exact setting I had to produce a report that only specifies previous day failures.