Illustrator won't save my files on my iMac

I recently updated to the latest version of Illustrator, and I can't save my files on my computer in any format. I can save the files on Adobe's cloud though, but I want to be able to save them on my computer. The "save" button is grayed out. The cancel button can only be accessed using key commands and not by clicking it. 

I've tried uninstalling and reinstalling Illustrator. I've tried installing an older version of Illustrator, but that didn't fix my problem. 

Has anyone else experienced this and how did you fix it?