Everyone - if you cannot activate your new watch through the app, then do this: (especially if not purchased directly from Verizon): First, close out of the watch app - you'll be doing this through My Verizon. Sign into My Verizon (I used the website) and add it as a BYOD. Go to Settings>General>About to get the IMEI number. After you type it in, VZ will recognize it as a watch and then go through the prompts to add it to your plan as numbershare. It will take about 30 minutes for your account, etc to update. Restart your watch and it will activate and you'll see it on My Verizon. I think this works because the system will automatically add the IMEI to Verizon's database as opposed to waiting forever for Verizon customer service to do it.
This worked for me for a watch purchased from the apple store and the activation fee worked out to $10 cheaper ($20 online vs $30 through the app).