Sorry about the trouble. The suggestion given above is correct, but if that doesn't help resolve your issue. I would suggest you to reset the preferences ((https://helpx.adobe.com/in/illustrator/using/setting-preferences.html) of Illustrator and see how it goes. Disclaimer: Please note that resetting preferences will remove all the custom settings, and Illustrator will launch with default settings. You can also take a backup of the folders in case you want to. Location is mentioned in the article.
If you need any further help. We'd be happy to help.