When I download and open https://github.com/SaschaWillems/Vulkan/raw/master/data/textures/cubemap_yokohama.ktx in PVRTexTool, it does not display any images. The image display area contains a single window, probably at the size of the base mip level of one of the faces, filled with grey.
I have tried the latest version 4.16.0. The previous version I was using had the same problem.
The cube map is 8.4MB so I won’t attempt to attach it here.