I think I’ve found a soultion, Did you use a texture or did you change the part too a brown? It won’t properly import if one part is colored it will make the rest of the colors black. The tree base. Not the image.
That’s a roblox problem, your model it’s just fine, in roblox studio change the leaves mesh transparency to 0.011 or 0.02 it will fix that black background, it will look a bit weird but you can’t do much more…