I updated my system software from Mavericks to El Capitan yesterday but encountered a problem where Mail would not open. The AppleCare advisor told me it was a known issue and suggested I return to Mavericks until Apple resolved it. He told me to use Time Machine to restore my startup drive. Now that I have done that, Knox needed my license to be added again and my vault is missing. I did use Knox to create a backup on a separate external HD but Knox does not show it so I can't Restore. How can I fix this?