QBCFMonitorService is an installation folder of the QuickBooks Desktop file accessed through the QBCFMonitorService.exe file. It helps users open files in multi-user mode and enables the company's workstation computers to connect with the server computer. To prevent it from stopping unexpectedly, you need to configure Windows and the third-party firewall if the communication is interrupted, restart the QBMonitorService.exe, and reconfigure the QB company files on a multi-user hosting set up on the server.

https://proadvisorsolutions.com/blog/qbcfmonitorservice-not-running-on-this-computer/