When my certificate identity expired recently, I had to renew it. This was completed successfully, but when I tried to build/run my new iPhone application, I got the following error:
Code Sign error: Certificate identity ‘iPhone Developer: xxxxxxxx’ appears more than once in the keychain. The codesign tool requires there only be one.
Ok. So that sounded simple enough and easy to fix.
I opened the Keychain Access (/Applications/Utilities/Keychain Access) and found 2 certificates under “My Certificates”. The expired certificate was marked with a Red “x”. I deleted that certificate and then tried running my app again. No success, and the same error message occurred again.
I checked all of the tabs in the Keychain Access, but still no success to find a second certificate.
I later found the option to show expired certificates (go to: View > Show Expired Certificates). I found the second expired certificate under the System tab.
Problem solved 🙂