Having trouble with a texture on an .FBX

I’ve imported an .FBX from Blender, I also imported a texture unwrapped from that model in Blender and sent through Gimp as a .PNG. When I apply the texture to the mesh all the colors get mixed into one and don’t stay in the image. I messed up the texture as a test and just made it red and white stripped and the mesh ends up as a giant blob of pink.
Anyone else had a problem with this?

Selected all vectors, smart unwrap and exported to Gimp as a .PNG
Used the layer and paint tools in Gimp to add color to the texture.
Imported the .PNG into Unity as a compressed 2048 texture.
Then when I assigned the texture to the mesh, it turned the whole thing white. So I painted the whole thing red and white striped to see what areas weren’t making it in and the whole thing turned pink.

Thanks for any help you can offer. I’ve never run into this problem before.