Listen server issues

So I recently got my listen server again, ports forwarded, static IP, and the server only worked once.

Any ideas?

Edit: I turned off firewall, still not working, the ports are forwarded, I have a static IP as said above, and as I said once again: One of my friends could join once and then it stopped working.

Firewall/antivirus?

God damnit, I forgot, well give me a “dumb” rating, I really deserve it.

Edit: Wait no, still not working.

Have you tried checking the port?

When using canyouseeme.org, make sure your server is running, as it cannot see if the port is open unless something is listening on that port

Don’t quote me on this because I’m not sure,

I believe it is something with source engine, for i’ve had a similar issue.

Simply restart your operating system.
(Or change the port that the server is using)
There’s some times of which I’ve only been able to run a server once, perhaps the engine is not unallocating the port?

The ports are forwarded, and I tried restarting.