Adobe Illustrator simply won't launch.
What version of Illustrator & OS?
Since you did not put more effort into describing your situation, best I can do is advise you uninstall using the cleaner and uninstall then reinstall.
I tried Illustrators 25.4.1, 25.4.2, 26 and 26.0.1.. And I think I'm using windows 10
I tried it and it didn't work
Sorry to hear about this trouble. This is has been reported by a few other users as well, and it was found due to the conflict with Trend Micro Antivirus. Do you have this Anti-Virus installed on your machine? If yes, please make sure that Illustrator is added as an exception in the app settings. I hope it helps!