disk I/O error
Upload image file with the file dialog or by dragging and dropping images onto the dashed region
Upgrade Storage
https://www.zotero.org/support/reporting_problems#provide_steps_to_reproduce But if you're referring to this error, this generally occurs when you've moved the Zotero data directory to a network drive or cloud storage folder. You should keep it in a regular folder on your local disk, ideally in the default location.