QuickBooks Error Code 6000 is an error experienced by users when they are trying to open a company file. It is composed of series errors and usually caused by different factors that are listed below: TLG file corrupted Corrupted QuickBooks installation file A firewall is blocking the connection Damaged company file Multiple users logged in the same company file The network connection is incorrectly configured QuickBooks Error 6000 | QuickBooks Error -6000