Do you use preferred seating? If so you may need to configure PT3 to know what seat you use, see the
Tutorial: Preferred Seating for details and screenshots.
Otherwise, please enable logging (Configure --> Options --> Logging Enabled and restart PT3) and attempt to import while playing for one full orbit then attach the C:\Program Files\PokerTracker 3\PokerTracker.log and C:\Program Files\PokerTracker 3\PokerTrackerHud.log files to a
support ticket and we'll look into what could be causing this for you.