QuickBooks Error 80040408 is an error that occurs when the user is unable to connect to the QuickBooks company file. The error message reads "QuickBooks is unable to open the company file. Please check your network connection and try again." This error is typically caused by an issue with the user's internet connection, or a firewall setting blocking access to the company file. If nothing seems to be working for you, call +1 855.738.0359 to talk to an expert for improved guidance and assistance.