I am getting the message
The identity 'iPhone Developer: Rxx Pxxx (xxx)' doesn't match any valid, non-expired certificate/private key pair in your keychains
Can the problem be that I am logging for a coumputer of a diffrent user?, and if it is the problem, is there a way to solve it?
You need the private key and the certificate to go along with it. You can export these from the computer they are on through Xcode's organiser window.