DIY projects that were made with older versions of the LabQuest SDK (NGIO_lib) will not be able to communicate with a LabQuest or LabQuest Mini 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:
In order to get you project working with the new driver, you can get the latest version of the LabQuest SDK from here:
You will then need to replace all occurrences of the SDK that are associated with your project with the files from the new version. The communication library is named NGIO_lib.dll, and is the probably the only file you really need to replace.
In the event that the new SDK is not posted, it is safe to use the file below (v1.101 first distributed with LP 3.11.)