The LabQuest Emulator will not be able to communicate with a LabQuest over USB if a newer USB device driver has been installed by another application. The newer USB device drivers were first distributed in May, 2016 by the following products:

While we have not created a new installer for the LabQuest Emulator work with the new driver, an existing install can be made to work by replacing a LabQuest communication library on your computer.

The communication library is named NGIO_lib.dll and is installed in the same folder as the LabQuest Emulator application. Typically, the NGIO_lib.dll is installed here:
C:\Program Files (x86)\Vernier Software\LabQuest Emulator
You will need to replace this file with the attached version. This version was first distributed with Logger Pro 3.11 and should never go out of date, with respect to the LabQuest Emulator software.