Made a custom character skin (normal 4 pixel arm) and downloaded it via png and made sure it was 64x64.

After selecting the skin map, Minecraft said make sure skin is a png and at either 64x64, 64x32, or 128x128.

Reloaded Minecraft, rechecked the image, made sure it was the correct skin, but it still tells me to check the image.

The only other thing I could think of is the image is too large (4 KB) but then why are there 128x128s?

Edit: only 4 KB, (used to say MB)

Edit^2: possible good info: I used a very old skin made on minecraftskins.com/skin-editor/ (pumpkin logo) then updated it (added a few new pixels) The original was 2 KB and the second one was 3.2KB, which somehow rounded up to 4KB in my Downloads before I clicked more info.