How can I correct a close reconciliation?

It would be helpful to understand what you did to make the reconciliation "work."

I don't know "Mac" Quicken, but in Windows Quicken you can "undo" a reconciliation by going into the register and changing all the Rs that show up under the "Clr" column back to blanks.  Maybe Mac Quicken allows that?

In the Windows Quicken world if you're out of balance in your reconciliation then Quicken proposes an adjustment - a "plug" number - to get things correctly stated.  If that's what happened in your case then the proper response would be to undo that adjustment - meaning your reconciliation now won't work - and do whatever you need to do to make it work.  That might include changing the reconciliation status of a transaction or transactions to "blank" or "c", it might mean you need to make some entry or entries in your register, or something else.