I have been trying for weeks to pair my apple watch2 to several different bluetooth speakers and a bluetooth earbud. I tried most of the suggestions listed hear and elsewhere. I always got a message indicating I should either move the bluetooth speaker or earbuds closer to the apple watch or make sure it was turned on in discoverable mode.
I finally found an answer:
Without deleting anything, un-pairing anything or doing any of the many other suggestions.
I put my apple watch in airplane mode by swiping up on the apple watch screen and selecting the airplane icon.
I then started the bluetooth device in discoverable mode, then on the apple watch went to setttings>bluetooth and turned on the bluetooth.
When the bluetooth device appeared on the apple phone bluetooth screen I selected it and voila it paired.
I then took the apple watch off airplane mode. It then paired w/o putting the apple watch in airplane mode..
This method worked with all of my bluetooth devices.
I hope this helps others..