So on the main site it says it is apart of the Car pass, I have the car pass and cant get it. Is the main Forza site lying or is this a glitch?
You don’t “get it” you will receive an update and the DLC pack, too. Check your game contents and make sure you don’t already have it. You can also look among the cars and see if you’ve all get some marked “New” and “Free” - that would be the pack (and game update) already installed.
Oh ok I just saw it was available for free under my buy cars menu. Weird how it says under the marketplace I need to buy it but thank you Snowowl!
When you have the Car Pass, those packs automatically come to us in FM5 on the Xbox One. We don’t need to institute a download from any other location. They arrive. 
While you have carpass you will get them free without having to buy the pack itself. Marketplace is more of a quick show of what cars are in the pass before we go get them so that we arnt scrolling thru trying to figure out what’s better in our list of cars.