Was PT4 working OK before, or did you just install?
It seems like you haven't entered the correct password - our default is "dbpass", but if you installed PostgreSQL manually, or it was installed by another application then you would need to enter the password which was created at that time.
Alternatively, you can remove the need for passwords as described here
(that was written for Windows, but I think the same change should work on Mac - you'll need to follow these directions
to edit config files though).