Hey there,
The signup process is not automated. It is reviewed on a frequent basis (usually once a week, but people are people). That means that the signup is not instant, but you should receive an invite within two weeks.
One problem that can occur is if you have an exiting invite which has already been sent in the past, the system will not resend the invitation, so you may need to search older emails to see if you have a pending invitation.
Thanks,
Dave
