Custom skins does not work (1.16.5)

Hello, 

I just bought Minecraft today and I downloaded the new version, I downloaded a custom skin and I uploaded it to the Minecraft launcher "skins section" and saved it, but when I played Minecraft I just had the default Steve skin.

I tried with 3 different skins in the Minecraft launcher, uploading it to my account at minecraft.net, updating java, and reinstalling Minecraft. But I've still got the default steve skin!

Please help!