Issue: "Error opening Illustrator file. (64)" error message appears -- if the file was saved from Illustrator 2020 (Version 24.0) in the Illustrator 2020 format (Version is set to Illustrator 2020 in the Illustrator Options dialog box).
Workaround: Set Version to Illustrator CC (Legacy) in the Illustrator Options dialog box.
I don't understand the workaround. I'm on windows and they show me a IOS setings window. I can't find it and it makes me mad...