I just spent the last hour in Blender trying to bake a diffuse texture from a model created with photogrammetry to a lo-poly model created in Blender. I checked and double checked every setting. I went back to tutorials that I watched years ago. I looked for new issues that might be caused by the latest version. I finally found the problem.
The software I use for photogrammetry is Zephyr. It outputs the textured models in several formats. The two formats that can be imported into Blender or OBJ and FBX. I chose FBX. I chose poorly.
No matter what I did, I could not bake the texture from the FBX model to a low poly model.
When I went back to Zephyr and exported as OBJ, all my problems went away.
Baking Textures in Blender
Simmer3D 