I am not new to this but I am unable to fix my signing identity from Xcode Version 6.2 (6C86e). When I click fix issue on the following message:
I fixed the issue by running Xcode->Preferences->Accounts then selecting the agent and clicking the Create button for each of the Signing Identities
For me to solve this problem I had to login to http://itunesconnect.apple.com. There was a yellow banner that kindof told me what to do. I had to go to Contracts, Tax, and Banking and setup the contracts there.
What worked for me (after accepting the agreement) was removing my apple ID from the account list in Xcode and adding it back in.
In my case the solution was:
"Your Mac Development Certificate for “your name” was not found on the Member Center. Xcode can submit a certificate signing request on your behalf. Would you like Xcode to do so now?
It's a propagation server issue. Wait approximately 10 minutes and it will be fixed.
In my case none of the answers worked - olegiv's answer came close but given that in Xcode7 Apple has removed the refresh button, that wasn't an option either.
Instead, downloading all provisioning profiles again worked: Xcode -> Preferences -> Accounts -> View Details -> Download All
Struggled with this for a while, hope that helps.