Having had this issue on multiple occassionsoccasions and resolving it by manually editing the MTL file with map_Kd texture.png
.
The cause ended up being that creating a Shader Node (Blenderin Blender 2.8) material with Image Texture > Material Output
wasn't enough for Blender to parse the flow graph for the texture details
, and it was necessary to create the material like this:
Image Texture > Principled BSDF > Material Output
.
Hope it helps.