Might be a corrupt .plist.
Some games utilize the overlay for party and matchmaking invites. If it is not enabled, the invites will not work. Steam allows screenshots to be captured in-game by using the default keybinding of F12. This feature requires the overlay to capture the screenshots. The screenshots can be accessed in-game by using the overlay as well. Steam is the ultimate destination for playing, discussing, and creating games.
Do a backup, preferably 2 backups on 2 separate drives.
Quit the application.
Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Select Library. Then go to Preferences/com.apple.systempreferences.plist. Move the .plist to your desktop.
Restart the computer, open the application, and test. If it works okay, delete the plist from the desktop.
The In Game Steam Overlay Requires Access Machine
If the application is the same, return the .plist to where you got it from, overwriting the newer one.
Steam Overlay Skins
Thanks to leonie for some information contained in this.
The In Game Steam Overlay Requires Access Mac Computer
Apr 4, 2017 9:00 AM