QuickBooks error 6123,0 usually appears while the user tries to restore backup or tries to upgrade a company file into QuickBooks desktop. The error displays ‘Connection to the QuickBooks company file has been lost’. It may show ‘We are sorry but QuickBooks can’t open your company file’. Perhaps it is one of the complicated errors for you to resolve. In such stuck situations you can contact QBSsolved at +1 (888)910 1619 and we will assist you. Also, you can try some simple troubleshooting.