When did screenshot with shift-command-4 stop working?

10.15.7 Catalina running - yes it is old... due to the WGA/SAG strike, I have not been able to get work and my industry has flooded the Atlanta job market. getting a new laptop was in the plans for 2023... As of a few days ago, I have been unable to screenshot anything on my Macbook - web pages to my own desktop. The cursor shows up, the click/capture sound is made ... nothing.. no preview, nothing in recents or download or desktop... what happened?