Super beginner here. I looked through the previous posts, but couldn't find this. I have a series of parallel faces (in this case a shower wall) that I'm trying to apply an image texture to. There is a shelf in the middle that has faces above and below it that won't accept the texture, yet it appears to that it has been applied. For these faces above and below the shelf only, the texture won't show in material preview mode. I have UV unwrapped all of the faces (I realize they are too small based on the image I'm using, but I was just using this to check, and truth be told I don't know what I'm doing with the UV editor very well yet). Any idea why?
I went in and re-UV-unwrapped it and it appears to be working now. Also the image I had in the UV editor was the wrong material from what I'd applied to that area. Not sure exactly what the relation is to the image in the UV editor vs. the one used in the background of the material, but this alignment appears to have worked