The issue seems to affect only certain games now. From your list the only games I have are Total War: Shogun 2 and LEGO NinjaGo Movie, and both fail to show up on Galaxy. And I have seen several people complaining about the Mafia games.

Company of Heroes
Company of Heroes - Legacy Edition
Company of Heroes: Eastern Front
Company of Heroes: Europe at War
Company of Heroes: Far East War
Company of Heroes: The Great War 1918
Company of Heroes: Modern Combat
Earth 2150 Trilogy
Entropy : Zero
Wilson Chronicles
Half-Life: C.A.G.E.D.
Rexaura

My Companys of Heroes (1, 2 and Legacy edition) show up in my gog galaxy 2.0.

Edit: If you install the missing games and play it, they will show up again on Gog Galaxy 2.0 (Steam), i tested with 10 secon ninja x, and it showed again on Steam in my Gog Galaxy 2.0. Don't know if works with the others.


Edit 2: It also worked with Polyball.

These are also missing in my library and some others :-)

If this is true you could also use SAM (Steam Achievement Manager) and start the game, it will show on your Steam that you played the game and it will fix it on GoG. I'm going to test it right now...

My missing games:
- Mafia 3 Definitive Edition
- Dragon Age Awakening
- F.E.A.R: Extraction Point
- LEGO NinjaGO

HOLY S*** THE FIX FROM @SonicScientist1987 WORKED!!!!! Here's the tutorial:

1-) Find the games that are missing from your GoG Galaxy Steam integration (yes you have to find them manually)
2-) Download SAM (Steam Achievement Manager, you can easily find it on google)
3-) Open SAM, Steam and GoG
4-) Go to https://steamdb.info because you need the APPID of your missing game
5-) Find the missing game on Steamdb and copy the code from the first line that says APPID
6-) On SAM put this APPID on the little search bar from above and double click the game image, a new screen will open, just close it and it will say on Steam that you played that game
7-) Now your missing game will appear on GoG

P.s: Dragon Age Awakening and F.E.A.R Extraction Point didn't work doing this, you can't even find these games using CTRL + F on GoG, it's like they were erased from GoG Steam integration database...

P.s 2:The fix worked for only a couple of minutes, the games are gone now and it's not working anymore using the SAM trick =(

you don't need SteamDB to find out your game id, it's visible in url on game page in browser, right after the game title.

Tons of my Steam games are still randomly missing from GOG Galaxy, including some that are currently installed. This bug is absurd, completely unacceptable, and obviously needs to be fixed yesterday.

Just looked at my Steam library in Galaxy 5 minutes ago and missing installed games have returned. As far as I can tell uninstalled games in the library that were missing have all reappeared.

I haven't done anything on my end. Haven't even reset the PC. So not sure if something has updated in the background.

Yesterday the new version 0.51 of the Steam plugin was released, and this addresses the issue regarding the games missing.

Source: https://github.com/FriendsOfGalaxy/galaxy-integration-steam/commits/master

My Steam game count is also back to normal (again). Let's hope the issue has been fixed for good!

Mine too.

All of my missing Steam games re-appeared shortly after my previous post a couple days ago, but now they've all randomly disappeared again for no reason. This is incredibly absurd. This issue needs to be permanently fixed yesterday. What on Earth is going on here?!

6 games of my Steam acount are missing in Gog Galaxy 2.0.


Edit: It when back to normal

Right now, my Steam game list is complete, but the number of games displayed in the Summary is wrong.

EDIT: The Summary also shows the correct number of games now.