I've tried everything that's obvious and did all the "normal" rook mistakes. I followed this guide which technically should have fixed the issue, but it didn't. It wasn't until I applied the base map to a regular sphere that I saw that the textures were working fine in Maya. They just won't apply to the model I've been working on, so the issue is with the model maybe, not the import? I've added the texture files for the "Amp" or the horn part that's black in the scene.