This error message typically displays when you are using QuickBooks verions 2011 or later and you try to open more than one QuickBooks company file at the same time. Beginning with QuickBooks version 2011, QuickBooks has restricted 3rd party applications from supporting multiple open QuickBooks company files in a single instance of QuickBooks. Note: SmartVault does support opening multiple QuickBooks company files in QuickBooks versions 2007, 2009 or 2010.
Error: 0x80040438. The application trying to connect to QuickBooks is not supported while multiple instances of QuickBooks are running.
If you use QuickBooks version 2011 or later, you must first close your open QuickBooks company file before you can open another QuickBooks company file.