Downloaded car design does not appear in car selection or my designs menu

I had some cars in Forza 5, Forza Horizon 2 and recently in Forza 6 where I downloaded a design for a car but it would not be permanent.
In Horizon 2 I remember selecting a design that would apply on the car but not to the thumbnail. I could drive races and championships with the design but when I switch for another car and back the design would be gone.
In Forza 5 I remember that I downloaded designs for several cars successfully, leaving the game and shutting down the console, on next launch some designs were missing. I tried it several times with one car, it was reproducible.
In Forza 6 it's a bit different (to Horizon, since there is no open world mode) and the design will not apply to the car at all.
In all of these cases I can find designs for all the other cars in the my designs menu, but not for these cars.
- Is there a solution?
- Which cars are affected?
Pictures about "Downloaded car design does not appear in car selection or my designs menu"



How do I use downloaded designs on Forza?
To add stripes, logos, and custom designs to your car, go to the Garage / Designs / Apply Decals menu to enter the Livery Editor.How do you put custom decals on Forza Horizon 4?
Forza Horizon 4 launching issues could happen when the game is not properly installed on your PC, or certain game files are corrupted or missing. In this case, reinstalling your game is very likely the solution to your issue: 1) On your keyboard, press the Windows logo key and type Forza Horizon 4.Why is Forza Horizon 4 not available?
Participate in street/circuit races Once you've completed between five-10 races you'll unlock 'Horizon Life' which you'll find in the menu.Unity Car Game Tutorial - Vehicle Select
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Erik Mclean, Maria Geller, Ono Kosuki, Tim Samuel