How to add textures to Dynamic Heads

So I have a model that I want to make into a dynamic head. I don’t have much of an idea how, so I join it to the existing RealisticMaleBody head, and delete the old head’s vertices. It works perfectly except for one issue. The texture disappears. I try so many different ways to add the original texture back, both in blender, and in roblox itself with no luck. I have also searched devforums, google, and many discord servers.

Heads with texture: image
Mine: image

Also textures do appear on the mesh normally.