That happened to me once because I accidentally added a space at the end of the code. My advice is to clear your cookies and try again, or just hit up the support chat. I was checking
https://wagertales.app/ and it seems that you must enter the code exactly as written in the cashier before you finish the payment. If it still does not work, the live chat agents can usually add it to your account manually in a few seconds. They are very helpful with these kinds of technical glitches. You can also check your "Bonuses" section in your profile to see if it was activated correctly. Once it is there, you can see your wagering progress and the max bet rules in plain English. It is a very transparent system and they really try to make things easy for the players. I have gone through all five stages of the package now and the codes worked fine every other time. Just double-check your deposit amount too, as the minimum is 20 EUR for the bonus to trigger. It is a fantastic deal so it is worth a couple of minutes of troubleshooting!
