Any tips for adding numbers to your SMS campaign?

I am trying to add a user to the SMS campaign (It has been Approved).  Sometimes it will add them, and it says “Setup in Progress,” but as soon as I do anything they drop out of the list and my user count goes from 33 to 32.  Most of the time, however, when I click Add, nothing happens at all.  I am not sure if the UI isn’t working correctly and my user is being added, but I am not being patient enough, or if there is a problem and the action just keeps getting terminated.  It shows in the log that I am adding someone, but they are not in the list, and definitely unable to send/receive text messages.  Soooo, any tips, or further insight anyone has would be greatly appreciated.