Code Sign error, How to switch an Xcode Project o

Question

I know how to use Xcode and everything but this is a beginner question. I just got a new MacBook Pro and I specifically got it for iPhone development. I transferred my main app project from my Mac Mini to my MacBook Pro so that I could work on both. It has all worked out well so far, but whenever I plug in my actual iPhone to test on, I receive an error with Code Signing. I spent hours researching the issue and even re-downloaded every certificate I had and Provisioning Profile but still nothing. In the Organizer everything is valid. I have made sure everything was correct in the KeyChain Access and made sure it was in the login section. I have restarted Xcode and my MacBook Pro, but still nothing. I have even transferred a copy of my whole Developers Profile from my Mac mini to my MacBook Pro. Now I'm getting an error

Code Sign error: No unexpired provisioning profiles found that contain any of the keychain's signing certificates

What do I do? I've tried EVERYTHING.

Answer 1

(on the old mac) open "Keychain Access", select the category "My certificates", find the one that says "iPhone Developer: Your Name", click the triangle next to it and it should expand to show you your private key. Select both the certificate and private key, right click (control-click), select "Export 2 items" (or File->Export Items). Save them somewhere, copy the file over to the new mac, and double-click on the file to import it.