Hello, well first of all I have to clarify that mojang technical support sent me here for help (I attach a screenshot).

Well my problem is that when I put a skin for Minecraft both from the launcher and from Minecraft.net when starting the game (being connected to wi-fi) in the single player mode I cannot see my skin that I have put before, I ALWAYS see Steve and even if I select Alex I can't see her It's always Steve, But recently (Today), I discovered that when entering a server my skin IS SEEN, while when entering my personal world (Single mode player) I CAN'T SEE IT.

It should be noted that I recently bought the Minecraft, about 3 days ago, last Sunday to be exact so I am somewhat inexperienced in all this, thank you and I would appreciate your help.