I uploaded a new skin; why did my skin not change?

I have recently made a new skin for myself in Minecraft Java Edition: 1.15.2, but the skin will only load up as the Alex default skin or the Steve default skin. I have checked on the internet to solve this problem in any way I can. I have legally purchased the game and my skin is in the right pixel size (64x64). I have tried updating it on both the Launcher and the official Minecraft webpage.