How many vertices does the model have. At that file size, it is possibly a large number. There was a roughly 65K vertex limit. According to the thread link below, larger models are now possible, but there are some importing issues:
How many vertices does the model have. At that file size, it is possibly a large number. There was a roughly 65K vertex limit. According to the thread link below, larger models are now possible, but there are some importing issues: