Okay, Hubs has just finished the process. He got the email, and it contained a link that said “click here to get started.” After reading through and accepting the terms and conditions, he then was walked through setting up a Glowforge™account and password, and now he’s able to access my machine.
I tried the same thing with my alternate email address, and got an email that did not contain the setup link – but then I discovered that I had apparently added that email account to my first machine, so it presumably already had an account set up, which would explain why it generated a different email.