Just updated my Illustrator today and Now I can't open a slightly older illustrator file.

[LisaLa]

Hi, I'm running Mac OS Big Sur 11.2.3 and I just updated my Illustrator app today and now it won't open some older files. I took the file onto the owners mac and it opened up fine. I did not update his illustrator. So now on this file all it does is sit there and spin till I get a Illustrator is Not responding. How can I get back to the previous version of illustrator I had so I can work on this file I have?

[Ton Frederiks]

If you go to your Creative Cloud app.

Click the All Apps option and click on the 3 dots at the right of Illustrator, you will see Other versions, from which you can install older versions.

But first I would try to reset your preferences.

[LisaLa]

What steps do I take to reset my preferences? And what will doing that do to my Illustrator app?

[Mike_Gondek]

[Ton Frederiks]

https://helpx.adobe.com/illustrator/using/setting-preferences.html