Originally Posted by
williemaykit
It may have to do with PayPal as an intermediary? I thought reward travel had to booked on an Amex rather than via an intermediary like PayPal. I could be wrong
Using an Amex 2 4 1 voucher requires you to use that Card, however I don't think it matters for normal reward bookings.
OP - I would be inclined to call BA if this is your preferred method of payment and it is still not working for you. Remember reward flights can disappear quite quickly so best to snap up those seats if you can.