If you are an antivirus/firewall, please add exceptions to them for these directories:
C:\Program Files (x86)\PokerTracker 4
After doing this, please reboot your PC and see if the issue is resolved.
If that doesn't help, then we may need to see your log files to help determine the cause.
You'll need to create support ticket here: https://support.pokertracker.com/support/ticket/176
In the ticket please provide your log files. Here's how you can send logs:
1. Enable Logging in PT4: Configure → Options → Enable Logging
2. Reproduce what you were doing when the issue occurred. When the issue occurs proceed with the next step.
3. Navigate to C:\Users\[WindowsUsername]AppData\Local\PokerTracker 4
4. Make a copy of your 'Logs' folder and .zip it.
5. If the file is too big to send, please upload it to to a cloud service like OneDrive, Dropbox, or WeTransfer.com, and share a link.