Quickbooks documentation did not work for me, but this did.
Sun Apr 05 2020
In Quickbooks Enterprise 2019 I could start in Single-user mode, but if I tried to start in multi-user I could not. I ran through every single utility in the QBTool kit to no avail.
When I scanned for the company file in the QB database utility, I'd get a message the QBDBMgrN was not running. In services.msc, the two main Quickbooks services would not start even after setting them all to keep trying after all consecutive failures. I also reconstructed the file.
My firewall ports were fine.
After reading this article from Quickbooks, and trying all of the recommendations, I resorted to uninstalling the application.
This still didn't work. I kept getting the same exact error when I tried to switch to multi-user mode. I realized that I had a bunch of Quickbooks files left over even after uninstalling so I deleted all of the files in:
C:\ProgramData\Intuit C:\Program Files x86\Intuit C:\Users\$userprofile\AppData\Temp\Intuit
Deleted all qb users on the server.
After reinstalling this still didn't work.
Uninstall with Revo Uninstaller. Use the advanced scan to check the registry and nuke all of the leftover QB garbage. Then reinstall the app. Hopefully this helps someone out.
Error 6175,0 QuickBooks was unable to back up your company file