I activated AW3 in minutes at home with Verizon. Things I think helped:
1) Call before you start activating and verify that your account is ready to add the watch. My account was only eligible for two devices and I already had a phone and tablet on the account. I had read the activation instructions and it said check on this first. The rep changed my account to accommodate 3 devices. Had I not done this first, the activation would have failed.
2) You will need to sign into Verizon mobile app during the cellular setup. If you don’t have a password already, download the app on your phone and register for a password. I did this right before I started. The password I created worked during cellular setup not my password used when signing in on their website.
3) Getting your AW3 working is a two step process. You activate then set up cellular. Read how both are done right here before you start.
https://www.verizonwireless.com/support/apple-watch-series-3/
The only problem I have experienced is my messages keep failing to send. I’m trying to resolve on my own and have not determined why they fail. I soon will probably call Apple.