Xcode 6 App Store submission fails with "Your account already has a valid iOS distribution certificate"
Got it solved by editing the iOS Distribution Provision Profile in the Developer Member Center.
For some reason there were 2 certificates to choose from for the Distribution Provisioning Profile. I switched over to the other certificate and I could Validate and Submit my Archive build for beta testing.
So, you may have more than one certificate for signing your Provision profiles. Make sure you have the right one (by trying all of them) and hopefully that should work.
I tried many things like Exporting Developer profile from Xcode Accounts and importing it in the organizer, installing the provision profiles from the member center, adding them to my keychain. But none of those worked. It started working only after editing the appropriate Provisioning Profile manually.
You could also trying removing all your available Provisioning Profiles and let Xcode create new ones for you. This will work too.
I also had this issue, which turned out to be caused by an attempt to export for ad hoc deployment using a development provisioning profile instead of a distribution profile. It seems this is no longer supported in Xcode 6.1. Once I created an ad hoc profile and installed that the problem went away. A more useful error message would have saved me hours of work and would be greatly appreciated, Apple.
This thread was helpful:
Besides all the other answers, there's one more possibility after 2/15/2016: the old World Wide certificate expired and I guess everyone has already downloaded the new cert (or check this out). However, you'll be seeing this error if you haven't remove the expired one. You may need to choose View -> Show Expired Certificates to unhide expired certs. If the error is still there, try regenerate provisioning profile as advised by the others.