Yes, this is an issue with pre-merger SPG bookings. I was unable to apply a SNA but was able to cancel, re-book the room, and then apply ok. Similarly, I could not cancel SNA from a pre-merger SPG booking, but when I cancelled the whole booking the SNA were instantly reavailable.

Also, and I cant find the thread I posted in before. There is still no way to remove an exisiting award certificate and reapply one for lower points. If you are trying to do this, do not let the agent do what happened to me, where they were able to remove but not reapply - so I had a booking with no award attached (this is spg legacy). One of the Lurkers has been trying to help but in the end (amazingly) availability at Xmas opened up so I could then cancel and rebook. FYI, this was the St Regis Punta Mita and I have been very impressed with their email responses and helpfulness around this. It is quite nerve-wracking playing around with reservations that show a $30,000 USD cancellation penalty!!

On other fronts my account now seems fully functional. I have done a number of transfers from AMEX that are quick.