That's unnecessarily vague, it makes me ask is it either

a) They have proof of the transaction but have decided not to share it. That would be a policy level decision to ignore the community, as such as it is represented by Gleb asking a pretty simple question. Why would they want to take such an opaque stance?

b) They don't have definite proof to offer, which in turn means
1) It didn't happen, the membership was never paid for and they ^^ are prepared to straight out lie about it
2) It did happen, but they can't provide proof because there is none to provide? If Bitpay can't or won't provide that info, is there any other way it could be done satisfactorily?