Creating a GoldSrc (Half-Life) engine server?

I can host Source game servers and 99% of all other games I own, but Half-Life engine games, like CS 1.6 and Sven Co-op literally don't work at all. Like, I can't even use localhost to connect to them. I've tried SteamCMD with HLDS and also just creating listen servers. I used to not have this problem. I have all ports forwarded for Steam and GoldSrc games, and the ports/games are allowed through my firewall. I've tried changing the server port and everything, I don't even get error messages in the console.

Anyone here an expert on server hosting GoldSrc games?

Probably not the BEST place to ask something like this, but I've found no answers so far on other websites.