How long did you wait for it to start? On a big database like you have, it may take some time to calculate the database.
If you try in a smaller database, do the notes process?
Something you can try is to reset your NC settings. It can help with things like this in some cases:
1. Close PT4 and navigate to: C:\Users\[WindowsUsername]\AppData\Local\PokerTracker 4\Data\AppsData\Tm90ZUNhZGR5.
2. Make a backup of the .xml files (copy/move them somewhere else on your pc).
3. Delete the .xml files.
4. Restart PT4, go into NoteCaddy and set your settings as you prefer again (File → Settings).
5. If you use Color Definitions, then import ColorDefinitions.xml that you backed up from step 2, into NoteCaddy → Tools → Import Color Definitions.
6. Reset and reprocess the notes (File → Reset Notes).