Well, it's pretty self explanatory. The background picture doesn't load, but it shows black like this. The license plate combination generator is fine, since the plate combination appears as it should in parts selector. It's probably some minor error in .json file, however I'm clueless what it is. Help is much appreciated.
Sometimes you just need to use a different license plate number and then enter what you want. If that doesn't work, you have to press enter on the text generator.