Needing help with setting up a server

[Sharktapuss]

Hey guys, just need a hand with setting up a moded server.. or any server for that matter. I have gone through the process of doing port forwarding ect and that (After a long and frustrating few hours thanks to my terrible internet supplier) is now working nice and smoothly, I have made the server and set up the course, the cars, and even the weather... But now I've run into a problem that I can't seem to find a fix for anywhere. When I open the server and get it running, and then go into the online section of the Assetto Corsa Content Manager and go to join the server, I am unable to join it and get the error ( Object reference not set to an instance of an object) and can't seem to find any way to fix this. I can open the exact same cars and maps offline perfectly fine but the second I try to join the server I get this error and the :join: button is grayed out... any ideas would be really appreciated!!!