Check out example codes for "has apple distribution certificate installed but its private key". It will help you in understanding the concepts better.
Code Example 1
Up to date (Jully 2020) (xcode 10 - 12) - go to Xcode - Preferences - Accounts - Manage Certificates - Click on the + at the bottom left, then Apple development - Wait a little, then click Done That's all. You may want to revoke the old certificat on developer.apple.com too. https://stackoverflow.com/questions/47256780/distribution-certificate-private-key-not-installed
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