How To Fix QuickBooks Desktop Error 6123? QuickBooks helps register all the transactional reports and data between different companies. While upgrading a company file to QuickBooks, opening a company file from a network server or restoring a backup, you may encounter QuickBooks Error 6123. You may be unable to restore the backup. In this article, you may find a solution to the error encountered. What is QuickBooks Error 6123 and How it is Caused? Sometimes, when a user tries to restore QuickBooks company files from backup hard disk or opens a company file from the multi-network server. After that, an error message “QuickBooks Error 6123,0” is displayed on the screen. QuickBooks error 6123 0 is caused due to: Restoring a company file from an external storage device. Disrupted network connection from the host server. Damaged QuickBooks Company data file. Firewall settings interrupting QuickBooks to open the company