If the QuickBooks Database Server Manager (QBDBMgrN) is not running on your system, then many potential reasons may have led to this problem. Some of the root causes include interruptions from Windows Firewall and antivirus settings, which prevent QB from accessing the internet. Moreover, the database or network may have become damaged or corrupted, the hosting settings might be misconfigured, or your QuickBooks installation is not complete or has been damaged.

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