To cancel the possibility to use Whatsapp from my Apple Watch was a good Idea !!!
When i boutgh my apple watch a guy in the Apple shop said me that: "whatsapp now receive only notifications but, in a while, you will use it fully"
It seems to me that we go back instead to go further.
Apple Watch, iOS 9.2
Hi
To receive notifications on Apple Watch from WhatsApp Messenger:
On your iPhone, in the Watch app, go to: My Watch (tab) > Notifications > under the heading "Mirror iPhone Alerts From", scroll down to WhatsApp Messenger > turn on notifications.
Also on your iPhone, outside of the Watch app, go to: Settings > Notifications > scroll down and tap on WhatsApp Messenger > check that Allow Notifications is turned on and also that Show in Notification Centre and Show on Lock Screen are both enabled.
I have the same problem as the OP but having already configured my settings as you suggest it is still the case that What'sApp does not notify me of new messages on my Apple Watch..
I also cannot find WhatsApp in the list of apps given my my iP6S settings for the Apple Watch.
Why Whatsapp disappeared on Apple Watch after installing OS 2.1
