The error message about needing email added was still there in both of my Velocity award bookings until a couple of days ago, so whatever fix may have been applied across the system did not (it seems to me) resolve the block on editing pax details. I have finally got the problem fixed for me by going to the SQ ticketing desk at Row 6 in SIN T3 Departures, and I now have full access to MMB for both the affected SQ PNRs. The SQ agent at SIN confirmed to me that an IT systemic problem had prevented contact details - phone as well as email - from migrating from my VA redemption bookings into SQ's own booking system.