Failed to verify the preflight file. It is not signed by Apple.

Please launch the Keychain Access application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad and start typing the name.

From the menu bar, select

Keychain Access ▹ Preferences... ▹ Certificates

There are three menus in the window. Change the selection in the top two to Best attempt, and in the bottom one to CRL. Log out, log back in, and test.