The development explaination

So called failed to launch game error bug on gog 2.0 explained.
I have seen a lot of bug reports involving the issues with launching games with GOG Galaxy 2.0 there a simple reason for it. The GOG Launcher uses the other launchers, Epic games, steam, Origin, Xbox and uplay. To send the command which starts the game in GOG Galaxy 2.0. GOG Galaxy 2.0 is a library the brings all your games to one place.

However, Games stored in the bookmark steam, epic game etc... are not tranferred to GOG launcher, just stored as a library. Anything that is in the bookmark GOG.com is on the launcher and can be launched.

The simple explanation

In short, you still need the other launchers (Epic games, steam, Origin, Xbox and uplay) to still play the games with GOG Galaxy 2.0.

How Playstation Network Connection works.

The development explaination
This is very interesting and very clever. The Playstation Network connection works list as a library at first look, but theres more to it. It locate through your other accounts of any games and then stored those game to the playstation bookmarker on your GOG Galaxy 2.0 Launcher.

Example of this; I have Mass Effect Andromeda on my PS4, but I also have it on my PC Origin account. So, it moved the game that was on the Origin bookmarker and place it in to the Playstation bookmarker.

As soon as I worked that out, I figgered GOG 2.0 devs must had used a clever bit of code find out, if you have the game twise or three times. It will list it as one game on the account you connected to the GOG Galaxy 2.0.

The simple explanation
It relocating your game with a account that you have connected to GOG 2.0 and moving them to a different bookmarker from your (Epic games, steam, Origin, Xbox, uplay and Playstation accounts)