Based on the description of the trouble you are having it sounds like your database cache needs to be rebuilt so if your database isn't that large (less than 1 million hands) please do this:
1. Close any open poker tables and poker site software and stop PokerTracker 4 imports if that's running (or wait for it to finish).
2. In PokerTracker 4 click "Database -> Database Management".
3. Click your database line then "Rebuild Cache -> Full Cache Rebuild". This could take awhile so schedule accordingly.
4. If that finishes without errors or warnings reboot your computer before trying things out again.
If that does not fix it, or if you have a large database, please capture this trouble you're having in a log file and then attach that to your reply:
Guide: How to Create & Submit a PokerTracker4.log File