Server disapears from list

I uploaded a game mode to my server, only to find that when i activated it, the entire server disappeared from the server lists. When i viewed the server info it just said not responding.
I disabled and went back to sandbox and it appeared again.
I have used the game mode on the server before and it worked fine (few months back).
Any idea what could be causing this!?

Can you connect to the server when the ‘gamemode’ is on?