ppavee: Here's something I found from these forums with a solution that worked for some:
https://www.gog.com/forum/general_beta_gog_galaxy_2.0/overlay_doesnt_work/post4 """
Go to
C:\ProgramData\GOG.com\Galaxy on Windows, or
~/Users/Shared/GOG.com/Galaxy on macOS.
Open the config.json file.
Add the following line to config.json:
"forceEnableOverlay": true
Make sure that all lines containing parameters with exception of the last one end with a comma (,).
Save the file and restart the GOG GALAXY client.
Now you can run your game and test the overlay by pressing Shift+Tab, even if it is not enabled globally.
"""
I used this:
{
"clientInstanceId": "080eb4f3-9b72-4395-a14b-949c4b030723",
"installationSource": "gog",
"libraryPath": "C:\\Program Files (x86)\\GOG Galaxy\\Games",
"previewBuildsEnabled": false,
"storagePath": "C:\\ProgramData\\GOG.com\\Galaxy\\storage",
"supportPath": "C:\\ProgramData\\GOG.com\\Galaxy\\support",
"forceEnableOverlay": true
}
And now it's working, thanks mate.