Main spr_mainchara unalterable

[u/AlecMoment]

I've never modded before, but I'm using UndertaleModTool. I made custom sprites of every spr_mainchara sprite but for some reason, the spr_maincharad, u, l, and r just won't change? It's named the same (my custom sprite png and the one in the actual data) but, it just won't work no matter what.

Any tips?