GMod wont start, Help plz.

So, my laptop that i originally had GMod on blew up. So i tried downloading GMod on my other computer. Now the thing is i downloaded GMod and tried starting it up. it went black (as it usually does when it starts up full screen) But instead of going to the main menu, Windows defender asked me if i wanted to keep blocking or unblock it. I clicked unblock because i wanted to use all of it. But then, it just shut down. Now, Whenever i click on it, It goes black, then just ends, no message or warning, just gone, WTF is the deal?