Photon server won't start(Version 5)

Hi,
I was using version 4 with no problems.I wanted to use version 5 but I got an error.

CService::OnException() - Exception: CManagedHost::StartApplication() - Failed to start application in AppDomain: 3 - 'Photon.LoadBalancing.GameServer.GameServerSettings'

What is the reason for this error? what did i do wrong ?