I downloaded this model. And I'm trying to add its textures. I get to the eyes and for some unknown reason the UV for it is just a tiny little dot in the very bottom corner of the image texture. I have tried to unwrap it and nothing happens. I tried to scale the UV and nothing happens. It just stays stuck there. This happened to a previous model as well. I merged two objects together and the UV for one suddenly turned into a small dot. Which makes no sense as to why. Other objects I merged had no problem at all. It was just those two objects.
Right now the problem seems to be just the eyes but I haven't gotten to any other part of the model yet to be sure.