macOS want to make changes.Enter an administrator name and password to allow this box keeps popping up

This box keeps popping up. I've read other answers to similar problem without success.

I've gone to keychain > system > certificates > my computer > certificate with an arrow > private key > access control (where I see written under 'name' com.apple.identity.export) and changed it to 'allow all applications to access this item. This didn't solve the problem. Can anyone help?

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