Error: extension .cer did not match expected (mobileprovision) – PhoneGap – Mac Step One Download your developer’s license from apple developers https://developer.apple.com/account/ios/certificate/certificateList.action Download mobile provisioning profile, if you have set up an app https://developer.apple.com/account/ios/profile/profileList.action Create a profile if you don’t have one. Create Bundle ID: https://developer.apple.com/account/ios/identifiers/bundle/bundleCreate.action Create Profile: https://developer.apple.com/account/ios/profile/profileList.action Step Two Open the certificate in keychain on your mac Step Three Right click on your developers certificate and export (iPhone Developers) Set password for p12 Here is video how to create p12 If you are on windows here is a video how to create .p12 certificate http://www.youtube.com/watch?v=4GteMgFvA1Y Step Four Go to phone gap > Signing Keys https://build.phonegap.com/people/edit#new-ios-key If you have already tried adding key and failed its good option to start over. Click on the secure lock and enter the password. This is the password you created while exporting your p12. Now click on add key button. Give a title and select p12 you exported and mobile provisioning you download from apple website. It should work from there.