My gmod server startup is not working someone please help

Just yesterday my gmod server stopped working it stops starting up the server when it reaches the point where it tells you your network and i kept trying to start the server up but it keeps doing the same thing then i found that there was no map running on my server and and i think that since there is no map running on the server the server wont start up but the problem is with that there is no map changing option in my server.cfg and i tried changing it through the server commands using the command changelevel<levelname> but then it says that the server isnt running can not change level can someone please help im new at having my own server