Originally Posted by paulo_crash
Yes this could be because of hibernation, since activated it leaves your server "offline" to save resources, suspend it let's say.
By hibernation I mean the server machine is running, but the srcds console says "Server is hibernating". I don't understand what that means, but it doesn't look like computer sleep mode.
And server shows online in server list in client find servers menu.
As far as I understand, there is no way to disable hibernation in CSS, but for now I solved this problem by adding a bot.