This information pertains to the original LabQuest.
If you have LabQuest 2 or LabQuest 3, see this article.
If a LabQuest is not recognized by a computer that can see a different LabQuest, or if the unit fails to recognize a USB thumb drive, the circuit board in the LabQuest that controls both USB ports may be broken.
If this is indeed the cause of the issue, due to a parts available, the LabQuest cannot be fixed.
See also:
My USB drive is not recognized by LabQuest. What can I do?
LabQuest with lots of data won't connect to a computer.
LabQuest won't connect to Logger Pro.