Ok. So we know that 5555 is set up properly and that it can divert.
Now we need to figure out why it's not diverting.
Check the Call Rerouting form. See if the phone has something other than a '1' in 2nd alternative field.
If it does, remove it. Then at the phone using the blue key, forward the phone on RNA to 5555 for both internal and external conditions. Then test it by dialing the extension number internally - not from the outside - to see if it diverts.
Ralph