*facepalm*
Ok, repeating slower:
1) Navigate to your VC:MP server installation directory (e.g. C:\vcmp).
2) Locate server.cfg file and open it with notepad.
3) Find a gamemode0 line (e.g. "gamemode0 gups") and change it into "gamemode0 mode" (default mode).
4) Restart your VC:MP server (vcmp-svr.exe).
5) If it doesn't startup, ensure you have mode.amx file in your gamemodes folder.