How to Solve QuickBooks 2021 Multi User Mode Not Working? Troubleshooting steps for QuickBooks 2021 multi-user mode not working issue. To access the feature, each user must have the QuickBooks License on their workstation. QuickBooks Multi-user mode not working is an issue that arises when the workstations try to launch a company file that is located on the server computer. At times, the error isn’t displayed, but QuickBooks keeps opening in single-user mode. Source: