Welcome to Inkscape Community!
Since I'm not familiar with Mac systems, it's a little hard to follow your video. After you select the file in your file manager, and click to open, then you should see Inkscape open with that file. I don't understand the part where you go to the menu at the top of your screen.
Would you be able to share the 2 AI files with us -- one that opens and one that won't open? Then we can investigate on our own systems.