I was happily working in InDesign 2017 when my job upgraded my laptop to Windows 10 and InDesign 2021. I cannot open the bulk of my InDesign 2017 files. There are no ID icons, only white boxes on the file names. I have tried everything under the sun. Copy file to desktop (which icon shows up) and then open from the desktop and/or from InDesign 2021 and I get notices saying that either the file is damaged or already open. I have tried Save As and Save a Copy with the same results. I have shortened the file name, because I seem to be able to open a few of my files with shorter names, but it's still an issue.
I know that I am not alone in this problem due to the amount of searching on the computer trying to find an answer.