I don't know about mods, but you must have did something for your mod, and then exported it, and whatever was exported won't be accepted easily. If you need to, take things out and keep exporting untill something works, then add onto that and export.
Maybe you made a simple mistake, if you delete a few things, and export, it might work. Then you can add back the things you had on. I don't have a clue on making mods, but I've had to make a model and export him a dozen times cuz of gay assimilate.
Why don't you explain to me what your mod is, and what you did for it?