This has been reported by some Spanish users as well. They're basically saying that they're spending tokens in new designs, and after chosing and saving one, they get out of the window, refresh the page and the new livery does not appear. Some of them say they cleaned cookies and cache but it wasn't working either.
Later in the race the new livery was showing up.
Reference:
https://igpmanager.com/forum-thread/15367 (Spanish)