I dont always have access to the internet and some times that coincides with wanting to play Gmod, however, lately any time I try opening the game without an internet connection so I can build something in singleplayer Steam will just kick me out saying “unable to connect to network” or something, even though I click run in offline mode. It never use to do this. How do I fix it so I can play singleplayer without an internet connection again?
You have to go into the offline-mode while you are connected to the internet.
After that you can disconnect your cable / disable the nic