Nearly every "unknown error" thread on Adobe Community points to corrupted preferences.
Corrupted preference files are the leading cause of "Unknown Errors." Resetting them restores the app to its factory state. Nearly every "unknown error" thread on Adobe Community
Select all artwork and go to Object > Expand Appearance . If that fails, try Type > Create Outlines to rule out font issues. 3. Artboard & Canvas Limits Nearly every "unknown error" thread on Adobe Community
Before diving into deep system settings, try these immediate steps: Nearly every "unknown error" thread on Adobe Community
Try saving a copy of the file to a different location (like your Desktop instead of a network drive). 2. Reset Illustrator Preferences
If you have plugins (e.g., Astute, CADtools, Pantone):