Adobe InDesign 19.5.5 won't open any InDesign files -- rainbow wheel

Hi everyone,

Suddenly this morning, my InDesign 19.5.5 (the most updated version I can use on my Mac Big Sur operating system) stopped working.

Specifically, the app can open. I can even create a new file and save it. But when I try to open any file (including a tiny file I created and saved and closed) it gives me the spinning rainbow wheel and freeze-crashes.

I've uninstalled and reinstalled InDesign 19.5.5 in Creative Cloud, and restarted the computer, but nothing seems to work.

Please help!! I've wasted 4 hours of my work day on this.... 😞