We have a Mac app in the app store. Upgrading to XCode 8 and Sierra has been a complete disaster. Couldn't get it to codesign. Tried some suggested remedies and apparently trashed our keychain. "Automatic" does absolutely nothing. Also found that "Reset" = "Revoke", not "Reload" -- How about some consistent nomenclature? Apple certificates web site shows nothing about "Revoke", although we did get an email.
Instructions in Documentation are archaic and have no relevance to current screens.
I never understood any of this stuff anyway, even though it worked in the past. Now I'm really lost. Surely, there has to be a better way.
The operation couldn’t be completed. Unable to log in with account 'XXXXXXXX'. The login details for account 'XXXXXXXX' were rejected.
No signing certificate "Mac Development" found: No "Mac Development" signing certificate matching team ID "XXXXXXX" with a private key was found.
(XXXXXXX substituted here)