I get "damaged file messages" on all my Indesign documents when I try to open them. I have reinstalled Indesign and it has not fixed the problem.
Is there a software issue?
Reinstalling rarely fixes everything - you can do a complete reinstall using the
Creative Cloud Cleaner Tool https://helpx.adobe.com/creative-cloud/kb/cc-cleaner-tool-installation-problems.html
Rollback to a previous InDeisgn version
Can you provide a screen capture of the "damaged file message"?
Also let us know more about your system: Please tell us what operating system (exactly) you're running. Please tell us (exactly) what InDesign version you're using.
Do you get errors from opening other kinds of files (for example, Office files like Word, or other files from other Adobe applications that you use?
Is it possible that your storage hard drive is damaged or corrupted? What are you reading files from?
One of those messages indcates you are not using version 18 to open at least one file saved in version 18.
If all of your files were saved in version 18 you are going to need to reinstall that.