watch will not power off

The first (and simplest) thing to try if something isn’t working right is to restart your Apple Watch and its paired iPhone. If necessary (device not responding), try a forced restart. Both methods can be found here:

How to restart your Apple Watch - Apple Support

Restart your iPhone - Apple Support

And;

Setup your Watch to a new iPhone

tried to pair with new iPhone 7. Got stuck here. Cannot power off using any method suggested online.

That watch isn't stuck it's syncing with the phone,look at the circle it's partially filled,this can take quite a while.