There are a variety of possibilities as to why you cannot redeem your code:
The platform where you're trying to redeem your code is temporarily unavailable due to a technical problem. This problem is usually solved within a few hours, please try again later.
You have entered a wrong code or you have entered the code incorrectly. Please check your entry and try again
You have accidentally purchased a code for a different platform which is not compatible with your account. Please check if you have purchased credit for the correct platform
If you still have issues with your code after having checked the points above, we would like to advise you to contact the platform's customer service. The customer support representatives can check why the code is not functionningas it should. They'll usually be able to resolve the issue right away.