Just to contribute, I have the same problem... I am a member, 4 days ago I received the information that my endorsement was approved but the system does not allow/provide the option for the payment of the $75.
In contact with support I was informed to make the payment via bank transfer, is that right? It is not possible to pay in any other way (credit card)
I am also getting the same error as stated above, it almost 10+ days.
ISC2 support inspite of knowing about the error, asking me to clear cache, use incognito windows etc.,
The excitement of achieving CISSP is started melting under sun