Thanks for the reply. Yes I have The below ports forwarded and authorized through the firewall. The program is allowed access in the virus protection. Just can't figure out why it drops off the server list after X hours.
16262 - 16272 TCP
Did you make sure that all the Steam ports are open? It could also be that if you have an antivirus software it could block those ports / the game server from accessing the specific query needed for the server to appear (would explain why its periodic since antiviruses can have checks every few hours)