As I said I have a problem, all my Indesign files from 2019-2020 have for some reason turned into Ai files that I cannot open, even though when I click on the file properties it states its an INND file. Of course if I recently opened the file in Indesign it will open if I click on it through the app, but I tried saving and saving as a copy, but nothing works. For some reason they all look like this
Right-click on the file and go to the Open With > Choose Another App menu. (Don't select InDesign if it shows up in the Open With menu--make sure you select Choose Another App.)Click the "Always use this app to open .INDD files" checkbox. Select InDesign from the list of programs. If ID doesn't show up, click More Apps; if it still doesn't show up, click on Look for Another App on This PC and look in the Programs folder.
The process is similar on MacOS:
Right-click on the file and ...