So I am getting the same error when trying to book any award on Air Canada. Were you able to eventually resolve this?
Or does anybody know what is the fastest way to resolve this?
I was able to resolve the same error by emailing them first my complete itinerary and then waiting for the call to make the payment. Not sure why I am not able to book online (my profile is completed with the PIN) but email worked for me. Took around 48h from emailing to having the ticket in hand; would have been faster if I had better cell service, but the call dropped once and you pretty much have no choice but to wait for the callback. All of their operators are disconnected from the payment system and it's a nightmare to find the person to make a payment.
It all worked out in the end, but you need patience.