I am not sure if that is a USA model, it says UK CA on the box. Does the warranty card say USA model? Nikon stopped servicing grey market items so that is important now.
I entered the serial number on the Nikon website and was able to see maintenance options. I have not seen a grey market lens in years. BH is an authorized Nikon dealer. I don't think they would sell lenses that can't be serviced.
p.1 #10 · FS: Nikon NIKKOR Z 800mm f/6.3 VR S Lens
Nikon no longer verifies if an item is grey unless it is shipped into the surface center . The center would then verify to determine if they’re gonna service it. Did you buy this new at BNH? If you did then, this is odd because thebox says uk on it. BNH doesn’t care where an item came from when they buy a used item from somebody.