I agree not always the best, but if that worked then maybe the original UV wasn’t exported from his 3D package or some settings were not correct on the export. Just something that can help towards diagnosing the issue.
As I do not use Painter or Maya I cannot really comment on the export routines and settings I’m afraid.
Good tip on checking the UV thought in the mesh viewer
Luck would have it, a recent post:
Not sure how relevant