I got a fall guys code for a skin but it wont work

I got it from the xbox gamepass ultimate

This might be a glitch then, because all users that come here on the community cannot see the skin on the PC version of the game, only on the console.

right there it says i can also use it on pc but i dont have the skin in the game

Where does it say it? Would you please share a screenshot?

Please check on your Microsoft account order history page if the code is showing as redeemed:

https://account.microsoft.com/billing/orders

The skin works only for the Microsoft account that redeemed it and only on the console. Unfortunately it is not valid for the PC version of the game.