Creating texture array contains only blank white image slices

I've been using a store asset that saves a texture array to the project. Until recently it worked perfectly and I have no idea what I did that broke it. To try to debug this I tried to create, and use other, texture array creation tools. Every one that I've tried, including my own solution, does exactly the same thing. It stores a blank white image in each slice of the array. I've tried to use different images, formats, compression quality, etc, and it did not help. I've even created a new project, with fresh new images, and default import settings and again the same result. It was working this morning and has worked fine for over a week. I don't know much about how it works so I kinda just tried anything I could think of. I've tried to look up my issue but I can't find any results for it. After some messing about with different images it still isn't working but I've noticed that some images come up plain black and others plain white. I don't see any reason for this happening as they have all the same settings. Perhaps it's the alpha channel? Otherwise I have absolutely no idea what's going on.

Any ideas?