I've seen a PokerStars bug where it can stop writing the Zoom seating files PokerTracker 4 requires when regular tables are opened. You can verify this for yourself:
1. Open this folder:
C:\Users\{Windows Login}\AppData\Local\PokerStars\Audit
If you do not see the AppData folder in Windows File Explorer then refer to
this guide.
2. With PokerTracker 4 closed start PokerStars and join one Zoom table.
3. Confirm seating files for the Zoom table appear in the folder in step 1 for each new hand (this is how PokerTracker 4 knows who is seated).
4. Open a regular table. Does PokerStars continue to generate seating files for the Zoom table? If not then unfortunately that is a PokerStars issue.
While I've experienced the issue myself in the past this doesn't currently occur for me so make sure you are using the latest PokerStars client.