Hi, Sarahbark! I hope my response is not too late! This is an old account and I've actually never posted before. . . I discovered this thread because I had the same problem. . . and I did something that fixed the problem for me!
-Go to Extra>Preferences>System Check
-Click 'Run Check'
-For me, the third parameter (FileTable contains needed files) failed the test
-Once it finishes running, click 'fix'
-Wait for it to finish (check the loading bar at the bottom of the screen to see progress)
-Restart
SimPE and Paul's Reaction Test Object should now appear in the object workshop
Hope this helps!