If you're not using v4.11.8 please update. PT4 Download Page
If you used an earlier 4.11.x version you may need to rebuild the database cache. Go to Database > Database Management and click Cache Rebuild > Full Cache Rebuild.
If you continue to have problems please open a Support Ticket
and report your problem
so that we can investigate further.
For future reference: please post PT4 issues in the PT4 section of the forum.