When many users are unable to access the company file at the same time, the message QuickBooks Multi-User Mode Not Working appears. Incorrect hosting settings, firewall restrictions, or network configuration issues are frequently the cause of this difficulty. It can be fixed by checking firewall settings, confirming hosting arrangements, and making sure QuickBooks Database Server Manager is installed and operational. Call 1.855.738.2784 to speak with the QB support staff if you run into any issues.