I export the model and upload the skin but it doesn't work and there is no change to my player in game.

Can you give a more detailed explanation or a video on how to apply the models please?

same

Here's my own log with the same issue. Forge, no other mods installed:
https://pastebin.com/sVWxe3ax

Can you post your minecraft log?

I loaded up the final skin file and it loads as it should. What is your Minecraft Name, And did you use the launcher or the website to upload your skin?

Can you post your skin file, that you exported?

WIP file, no gist:

"Final" file, using gist:

My MC name is no_space. I've used both the website and the launcher to upload the skin, with no change.

Could it be a MC/Forge version issue? I'm running MC 1.16.5 and Forge 36.0.15, I'd like to try the same setup you have to see if that resolves it.

I managed to fix it. The issue was with vanilla's skin filter not properly copying transparent pixels, and it corrupted the model data.