Just to make sure, are there files in the Folder »3DLUTs« in Photoshop’s Presets Folder?
What have you done for trouble-shooting so far?
Yes, there are. I've tried to uninstall, re-install and even install the 2017 version.
Have you reset the Preferences yet?
What is the complete Path of the »3DLUTs«-Folder?
Is the image RGB?