Nobody can connect to my counterstrike/gmod servers

I've been trying to fix this for quite a while now, I've portforwarded the ports but the main problem is port 27015, I can forward other ports but no matter what I can't get it open. On whatsmyip.org all my other ports show up closed (which is normal), but 27015 shows up as Timeout (blocked). Any ideas? I really need help on this one.