Minecraft Bedrock on Android won't accept valid skin; account mismatch.

I'm using Minecraft Bedrock Edition on Android, and I'm trying to upload a custom classic skin from my gallery. The skin is a PNG file with correct dimensions (64x64), but Minecraft keeps giving me an error saying it must be a PNG file sized 64x64, 64x32, or 128x128, even though the file already meets those requirements.