I was hosting my listen server without any problems, for several weeks (maybe months). I opened these ports:
1200; 27000-27015; 27020-27039; 26901-26901; 27016-27019 (all TCP/UDP)
But recently, my game crashed, leaving no error message. And I didn’t start the server again that day. The next day it just wasn’t working and my friends couldn’t connect. I tried to disable my firewall but no help. The IPs in my ipconfig seem to be the same ones, but strangely, both CSS and GMod isn’t working.
I checked my ports online and none are opened, my router is Zyxel P-660HW-T3 v2. The IP at my ports is the IPv4 one