Not enough information to offer an answer, (like I would know anyway).
Review the GPL FAQ.
Go thru install readme files point-by-point and confirm accurate install.
Think these mods require specific tracks be in their season folder, so make sure of that.
Confirm GEM+ configuration...
Recent forums search for "not working" revealed 114 responses, (seems not very many actually).
1. Start there, check and confirm everything relevant.
2. Keep a record of what was confirmed.
3. Post that so anyone who might respond has more info to go on.
Just a note...
Both the GT Sports Car Mod and the Can Am Mod installed perfectly on first try with my rig, and have always worked flawlessly, so never had an issue with either.
One reason, (no idea really as I understand it should not matter), might be because of making separate installs for each, by creating folders for each on the C drive, installing a fresh, clean GPL/1.07 install, then adding the mods to that.
Then it was just a matter of configuring/pointing GEM+ and it all works fine. If it doesn't, at least where things are wrong is known and other things are not messed up or the reason.
So, guessing the problems are that something in Windows is not set correctly, something went wrong with installs, or something with GEM+ is mis-matched...or...
The more info, the easier it is to narrow issues down to cause.
Edited by John Woods, Sep 14 2015 - 08:49 AM.