Pairing Oticon Opn hearing aid to an Apple Watch 2

How to pair my Oticon Opn hearing aid to my Apple Watch 2?

Although I have: (1) installed the "Oticon On" app on my iPhone 6S and AppleWatch,

(2) tested the operation of the "Oticon On" app on the iPhone 6S,

(3) checked the compatibility of the AppleWatch 2 with the hearing aid on the Oticon website,

(4) repeatedly unpaired the AppleWatch and the iPhone, as it is often recommended on the different forums consulted,

(5) reset the AppleWatch so that the available space is maximum (3GB of free),

the AppleWatch still does not detect my hearing aids.

Is there anything else to do?

Thank you in advance for your answers

iOS : 13.1.3

WatchOS : 6.1