Things that catch most people are...
1.) You need the v81 firmware or higher
2.) Once you set the MAC address in RPS you have to default the phone for it to make contact
3.) having https configured and a ssl cert that isn't public or the phone has ssl disabled
You can view attempted connections in RPS to make sure the phone is even trying to contact RPS to narrow down the problem.
We rely on this for all our installations and it's great, allows us to drop ship from the distributor to the customer.
~Bigbear
www.ulingo.com