Why can't I use the Lamborghini #63 Squadra Corse Huracán?

This car was given away to everyone as a promotional car to celebrate the Forza Liveried Huracan in real life that ran at a real life race.

However, the actual car still needs to be purchased from the Car Pack that includes it, which is the Motorsports All Stars Car Pack. Once you've purchased the pack/car, you should be able to drive the #63 currently in your garage.

For some reason, the gift Huracan is not correctly linked to the store.

Here it is in the store https://www.microsoft.com/en-gb/p/forza-horizon-3-motorsport-all-stars-pack/9nblggh4rlgl?activetab=pivot:overviewtab