Hello Qstor,
When downloads have exhibited this behavior, it often takes more than the usual amount of clicks to get them going. You may want to try using the "trouble downlaoding this pdf? click here" step. This button will set it back to personalizing to fix any potential problems and hopefully finish the personalizing process. Click to get it personalizing, click again and it should display "Ready!" and ask you to click once more. Click again and the product should start downloading. As I said, you may have to click the product a few extra times if it's being difficult or taking longer than usual to personalize, but go ahead and give this a try and let us know if it keeps giving you problems.
If you provide me with the name of the asset that is giving you problems, I can take a look at that specific one if the issue persists. Thank you!