Hi, colleen. I think I can picture the problem that you are having.. I'm no expert when it comes to modding, but I can understand the concept of how to create a mod somehow on the tutorials that read on the net. I actually experiencing the same issue on my other PC, but this mod works great on my main PC. Correct me if I am wrong, Davo. I think the problem is the .big file was created for 1.9 version of RA3, is this correct? Which means that the mod will fully work if the game will start under 1.9 version. Colleen, I suggest that you request Davo to recreate, or rebuild the mod or the .big file of this mod under 1.12 version. He will can help you on this.. he's a great man!
and also, colleen, once the mod works for you and you friends, I wnna join you guys playing this mod if you don't mind! That'll be fun!