User gets an error while trying to use Integration Settings or trying to sync data between BillQuick or ArchiOffice/EngineerOffice and QuickBooks:
“The application trying to connect to QuickBooks is not supported while multiple instances of QuickBooks are running."
QuickBooks 20xx has given users flexibility to open two databases at a time, i.e., primary database and secondary database, thus maintaining two connections at a time. If you opt for this feature and later try to sync data, say from ArchiOffice/EngineerOffice or BillQuick to QuickBooks, you will encounter this error because multiple instances of QuickBooks are running.
Currently, users do not have any option to choose which QuickBooks database they want to sync with. Hence, we do not support integration process when multiple instances of QuickBooks are running. For data integration to work, you have to run QuickBooks in a single instance mode rather than dual instance mode.