iPhone app signing: A valid signing identity matching this profile could not be found in your keychain
I had the same problem: I first downloaded my certificates to my small MacBook while on the run. When trying to install the certificates on my iMac... then I ran into the problems described on this page.
After spending hours pulling my hair out like many of you, I performed the following steps to fix it:
Close all your stuff except your webpage that should be logged into App Dev center.
Open Xcode. Click WINDOW > ORGANIZER. Then click the Devices tab and select "Provisioning Profiles" on the left. That should bring up your provisioning profiles. Highlight one by one (if more than 1), right click and delete profile. Yes, just do it! Delete them all! (I kept making a new one after a new one trying to make the thing work.)
From the first page you see after logging into the App Dev Center on the right side click "iOS PROVISIONING PORTAL" > (do not "launch assistant"). Instead click on the left side. Select CERTIFICATES. You will probably have just one line listed with your name/company - from there click on the right side REVOKE. Click OK to verify that's what you want to do.
On the same page click DEVICES. Click the box next to your device you are trying to provision and click REMOVE SELECTED. Again click OK to verify.
Wait about 2 minutes to let Apple do their thing.
Now click on "HOME" that is on the left side navigation.
Click "Launch Assistant"
create a new app ID - call it whatever you want. Just make sure it's unique enough to know that's the one you just created because the others you've been messing with all day will not be deleted from Apples Dev Center.
You should be able to follow the rest of the Assistant without troubles -- the main thing is you just had to delete your old provision profiles and start over.
Good Luck!
I encountered the same issue. This is because the private key of the certificate does not existing on your machine.
If you are now using a new machine and download the certificate from website: You can export the certificate from the old machine and then import on the new machine.
If you share the developer account with someone: You ask the account owner to send you an invitation and become a team member of that account. Then you can create your own certificate from scratch.
If you don't want to handle all these sh*t: Just revoke the certificate on website and delete the copy on your local machine. Then request a new one. This should be the ultimate way for solving such issue.
Had the same problem yesterday. Now, after signing to the developer portal, for every invalid provisioning profile have a button "Renew". After renewing and downloading updated provisioning profile all seems to work as expected, so problem is definitely solved :)
Update: you may have to contact Apple to get a "Renew"-button, or they removed it -- and the solution is to just download it and add it to the keychain, no need to renew.