I just wanted to follow-up here.    The SIM we were using had plenty of available data, but it was a pre-paid plan that wasn't specific to "hot-spot" data.    I had a hunch that @PhilipDAth was correct, and I got a new SIM card with a hot-spot data plan, and it's working great again.   I really appreciate the assistance and suggestions provided by the community.    Cheers. ... View more