I had a terrible problem, one day just stopped starting Illustrator, I decided to update to the latest version, began to appear an error and an offer to either start diagnostics or run the program itself, once after choosing the second option, it grinds to start, I reset, closed, and then either just a line in the task manager, or randomly opens the diagnostic offer (when you select it all just hangs) I tried reinstalling, through folders cleaned the settings through adobe creative cloud cleaner - well, already tried everything. Help
Sorry to hear about your experience. Would it be possible for you to share the version of the OS & Adobe Illustrator?
I see you've tried troubleshooting which didn't help. I'd suggest creating a new user account on your machine and try using the apps there. Let us know if it helps.
If it doesn't, I'd recommend connecting with Adobe technical support. Please click on the chat icon at the bottom of the page to begin the conversation. Team here would be able to perform remote troubleshooting and assist you accordingly.