Hi - as of today (22 Oct 2020) my Illustrator cannot open .aix files ("unknown format and cannot be opened") as in the screenshot. I think this is related to an Illustrator update to 25.0. I can't figure how to resolve this. I'm installing on my desktop computer, I'm the administrator. I'm signed in both to my Adobe CC and ArcGIS accounts. I have re-installed Illustrator 3 times now, and the extension several times, too, trying different parameters.
My standard install is downloading from the ESRI AM for ACC website with default folder locations and selecting "Anyone who uses this computer (all users)". I can see the extension installs files into what I believe is the correct folder (I've attached a Windows Explorer view of it). I think this remains the correct folder because I tried installing a random (and free) extension from the Adobe Exchange website (EAN13 Generator, it apparently makes bar codes) and it installed to this same folder and can be seen in Illustrator just fine (at the bottom of the attached Windows Explorer view as "com.mslv.ean"). The second screen shot is from inside Illustrator, having clicked Window - Extensions. I can see the new "EAN13 Generator" but what I really want to see is the ArcGIS Maps extension so I can continue my work.
Hoping there's an easy solution -- Ken