RMVX: CAN'T IMPORT SPRITES

So I'm working on some character sprite graphics for RMVX. I've been making them in Paint.net and saving them as .png files, and up until just now, I could import and use them as charsprites just fine. However, for some reason, whenever I try to import them now it just goes straight into the resource folder - there is no popup option for me to pick transparencies - and when I try to use the file as a charsprite, it appears to be completely blank. That is, I can't even click to a select a portion of the image to use as a charsprite, as though there is no image.

I've tried saving multiple different copies, as well as saving it as a paint.net PDN file and then saving a new PNG from that. I can't figure out what changed about the image!

Edit: Derp I figured it out
For some reason it was still a .pdn file but appeared to be a .png
FIXED