I have an .ai file. I worked with it around couple months. Yesterday I opened my file and saw: “An unknown error has occurred“.
I'm using Adobe Illustrator CC 18. I need to know about some software or methods for restoring .ai files.
Recovery is possible when the option was configured prior to the accident. In case it wasn't configured, then I recommend you follow the steps provided by the Adobe developers. Use the information on the URL posted below.
Adobe Support: https://helpx.adobe.com/illustrator/how-to/recover-files.html
Additionally, install Recuva and configure it using the built-in Wizard to recover the original AI file from the partition where it was stored.