Please ensure you have followed ALL the set up steps correctly and are using the latest version of Sidequest. https://sdq.st/setup - specifically make sure you have enabled the developer mode.

One of the most common reasons why your quest isn't recognized by SideQuest is you haven't given all the permissions in the headset. After you connect your Quest to your PC and start SideQuest, put on your headset and allow ALL permissions - in addition to file transfer you also will be asked to allow USB debugging.

If that doesn't happen, try different USB cable / port on your computer.

Here are more tips on how to solve this issue: https://sidequestvr.atlassian.net/servicedesk/customer/portal/1/article/540540968?src=1585010134