Originally posted by Dr1fter808
Okay, it works if I launch the postgre sql before PT4, but I don't understand why I have to do this sometimes to get the PT4 launched.
Sometimes the process that provides the postresql service fails while running and needs to be restarted.
On your PC hold down the windows key, and tap R
You will see this dialogue open:

When you press enter, you'll get the services control pane:

If the postgresql line does not say "running" and "automatic" you can click "start" or "restart" in the left-hand panel. If the service is running, use "restart", otherwise use "start". They system may detect that it is running when it crashes without informing the services control manager.
If the "startup type" column contains anything other than "automatic" the right-click the line and choose "Properties". You can set the startup type in there. There are two choices "Automatic" and "Automatic (delayed start)". Just the plain Automatic is what my system uses. You will (or should) only need to do this once.
BTW the above was done in Windows 10