Thats what they said to me!
Mine is from 2015...
I do have a receipt from the place I bought it from last year.
(Ive just checked the message I had from them )..it says
"To help us process your enquiry, you can upload proof of purchase for your watch, for example an original receipt or invoice (but not a warranty card)."
In fairness then, maybe the receipt from when I got the watch may have sufficed? As in they mention an "invoice"?