Installation was successful. I was even able to run postgres a few times but after a couple of restarts the error: "Windows could not start the postgresql-x64-15-PostgreSQL Server 15 service on Local Computer
Error 4551: Your organization used Device Guard to block this app Contact your support person for more info" started to appear even during manual startup of the service.
pgAdmin executes correctly but shows an error that it couldn't connect to the server
You are writing to the wrong people. As the message says "Your organization" setup a policy, contact them.