dedicated server issues

My friends and i made a server, all is smooth but everytime we all log off the game and we keep the PC on overnight (so the server stays open). The next day when we try to join the server, it goes failed to connect and then we have to restart the server to be able to join again.

Anyone know what might be causing the issue? Or how can we fix it?

PS. We disabled the sleep mode on the computer so it could really stay on.