The quickbooks error code 6123 is commonly caused by one of the following factors. The primary computer's network connection is broken. A port required to interact with the server... moreThe quickbooks error code 6123 is commonly caused by one of the following factors. The primary computer's network connection is broken. A port required to interact with the server holding the corporate file is being blocked by the network's firewall. QBW files that have been damaged. Data or software files in QuickBooks are corrupted. Depending on the cause, you can fix the error using QuickBooks Tool hub, QuickFix my program or File Doctor. However, make sure to investigate the cause first.