Server disappearing off the master list

I have had trouble with both my listen and dedicated servers. They will appear on the master list after I create them, and people can join them, but after about 5-10 minutes, the server will disappear, and people won’t join at all after that. I couldn’t find much help throughout the forums; has anyone else had this problem?

SV_LAN 0
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[editline]11:49PM[/editline]

Holy shit, I just noticed that you have one post.

I did them both, because the server does show up, but only for about 10 minutes.
I can host an internet game, I just can’t make the master server keep it on its list.