Scenario:
When QuickBooks Integration Manager is launched, an error shows up: QuickBooks can't start because it is already running. Only QuickBooks Accountant and QuickBooks Enterprise can open more than one company file.

When we click on OK to this error, another error shows up, QuickBooks is not open. Please open it and then try again.

Both these errors show up, when the QuickBooks company file is actually open and is running in Single User Mode only and the user is logged in as an Administrator for the system. Even the company file is not shared on any other system.

Resolution:
This issue is caused by the UAC not allowing QuickBooks Integration Manager to establish a connection with QuickBooks company file, although the QuickBooks has granted permission for QuickBooks Integration Manager full access.

To resolve this issue, bring down the UAC control level to Nil by following the below given steps:

  • Type UAC in the start menu or Control Panel search box.
  • Then click on the Change User Account Control settings.
  • Drag the slider to the last level (at the bottom of the scale).