I’m sorry that your chosen payment methods aren’t working for you right now. For launch, we were only able to implement one payment solution and a handful of users have reported problems with it. If you have another payment method, that would certainly be your quickest solution to getting UE4.
Otherwise, please contact billing@unrealengine.com and we will happily notify you when we roll out additional payment methods for you to try. We are actively working on these as I type this, but I can’t give an exact time for when they will be released.