QBCFMonitorService Not Running can prevent QuickBooks Desktop from connecting properly to company files in a multi-user environment. The issue may be related to the QuickBooks Database Server Manager, Windows services, firewall settings, or an incorrect hosting configuration.

Start by restarting the QuickBooksDBXX service through Windows Services and confirm that its startup type is set appropriately. Then verify Host Multi-User Access on the server computer, update QuickBooks Database Server Manager, and check firewall permissions. If the problem continues, use QuickBooks Tool Hub > Company File Issues > QuickBooks File Doctor to diagnose network and company-file connectivity problems.
Check: https://dataserviceteam.com/qbcfmonitorservice-not-running/