Hi theloon, I'm going to investigate this issue. Meanwhile, can you tell me the size of the PNG's you're trying to load and how many colors it has? Thanks!
I downloaded your program and extracted it to a new folder. Same deal on attempting to load a .PNG sprite. Tried 256 color at 240x240. Tried 16 million color at 64x64 and 16x16. Same error. Running Win 10 2004 with Nvidia 2060. Palette .PNG was 8x128 at 256 and tried another at 16 million colors. Both had 16 unique colors. That part works. Er, I mean. I don't think your program is buggy. Just something it doesn't like about my configuration. :)