If you are using QuickBooks Pro/Premier/Enterprise on the desktop, you may get the following error in the Method Sync Engine when attempting a sync:
Warning: Error in OpenConnectionBeginSession.
You cannot make multiple successive calls to the
"OpenConnection"method. Call "CloseConnection"
before calling "OpenConnection" again.
Resolution
This is due to the number of QuickBooks processes which may be running concurrently. In order to resolve this, please shut down every instance of QuickBooks.
Shut down the Method Sync Engine.
Open Task Manager.
In the Task Manager, shut down all instances of QuickBooks.
Launch the QuickBooks and the Sync Engine.
Failing this, please restart the computer.