If your Account at CRA is locked due to unsuccessful netfile attempts, please call CRA helpdesk to unlock your account:
CRA Helpdesk Phone: 1-800-959-8281 (Canada and United States)
For service hours, please check CRA contact page.
Usually CRA system will display error messages if the netfiling process fails. Please fix those errors in your return before trying to netfile again after your account is unlocked.