ERROR occured on animate: Unknown error while generating motion

1 the unknown motion error is that you adjusted the model scale... i can tell that just my the way his feet pock into the floor in your screeengrab

2 to repair the error i upscaled it by 10 and put it back into the rig

i assume you want a working models so will give you a T pose to work with but if you are making animation then every model in the set must be to the same scale i.e, use the same base model for all animations don't try to mix old with new