Cornelito de la Pampa

Hi all - I just wanted to say that tmittleman's solution above worked for me. At first, I manually added the Skitch application under System Preferences / Security & Privacy / Privacy / Screen Recording /... by browsing to the Applications and picking Skitch.app. It made me restart Skitch, after which I noticed a prompt from the system telling me that "Skitch Helper" wanted permission to record the screen, which I allowed. After another restart prompt and me manually restarting the Skitch app again, it started to work. Thanks tmittleman.