This is the real dead of this fabulous game that rFactor2 is..... this message "unknown base mod to be installed" is a nightmare... I have it in so many servers and it was the case that didn't allow me to perform a league race.... I was so disgusted... and then to sum up the only answer was : uninstall the mod that cause this message.... : but I don't now which one(s) ......... so I little by little am leting this game in standby.... and am playing ACC just because it's simple to play in multi.
But the feeling is not the same :-/
So, does someone have a solution about this issue ?