Sorry about the trouble. I would suggest you to try the following steps:
Close all Adobe applications and go to Location C:\Users\user\AppData\Roaming\Adobe Rename Adobe Illustrator and Adobe Illustrator 26 Settings folders to Adobe Illustrator.old and Adobe Illustrator - 26 Settings.old Disclaimer: Please note that renaming preferences folders 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. The location is mentioned above.
Rename the CEP folder to CEP.old from the following location: C:\Program Files (x86)\Common Files\Adobe
If that doesn't help, rename the UXP folder to UXP.old in the following locations: C:\Program Files (x86)\Common Files\Adobe C:\Program Files\Common Files\Adobe\