If you installed PostgreSQL manually then you will need to tell PT4 what port number and password you used. PT4 should still be able to start up connected to the original PostgreSQL service, unless you removed that.
If you previously had PT4 connected to a different PostgreSQL server then you will need to edit the configuration file to set the new parameters.
Go to:
%LOCALAPPDATA%\PokerTracker 4\Config
..in Windows Explorer.
Open "PokerTracker.cfg" in Notepad.
Find the [Database] section and update the port number and password that you used when you installed PostgreSQL.
Save the file, and run PT4 again.
If you still have problems, please open a
Support Ticket with a link to this thread and a detailed explanation of what you uninstalled and what you installed, and one of our support techs will work with you to get things working again.