As I am far from certain that I will ever use ANY of my SNUs, and am certainly in no hurry to try to do so, I went through "normal" (?) channels to claim my missing one (arising from Accor's belated crediting of my December 2019 stay). I emailed Customer Care on January 12, received a response from them on January 29 telling me my request had been forwarded to the technical team, and on February 25 had a response from them advising me that the missing SNU had been credited--which, upon checking, I confirmed was indeed the case!