When connecting the Reach Reporting Desktop connector to QuickBooks Desktop, occasionally you may see this "Can't Open QuickBooks" message:
We see this error even when just one company file is open. Basically, QuickBooks has opened too many versions of itself up and can't close those back down successfully.
If you close QuickBooks and the desktop connector, you will then run both as administrators. To do this you will right-click on the desktop shortcut (or on the app in Start Menu for Windows), then select the "Run as Administrator" option.
If running as Admin doesn't solve the issue at first, you may need to try the troubleshooting steps below:
Open your computers Task Manager (right-click on the taskbar at the bottom of your computer)
Navigate to the Details tab looking for multiple instances of QuickBooks processes running.
The QBDBMgrN.exe is the culprit here in the Details tab.
Select any record of it and click on "End Task".
Once that has been completed, you can re-open QuickBooks and the Desktop connector and run both as administrator. And then proceed with the next steps in your connection.