Causes: Damaged or unsuitable USB cable or USB port, or missing drivers.
Solution: Try a 3-foot or shorter USB cable. Long and/or custom USB cables can impact device connectivity at some USB ports. Avoid boutique 'audiophile' cables. The official Universal Serial Bus specification dictates a 90-ohm characteristic impedance; boutique cables may or may not conform to mandatory data specifications.
A different USB port or powered USB hub can sometimes help.
All JDS Labs DACs utilize standard USB Audio Class 1 drivers packaged with Windows and OS X. Some OS X 10.11 users have reported difficulty connecting USB DACs until installing all OS updates and rebooting. Rarely, some Windows users have encountered OS installations which are missing these standard UAC1 drivers. If your DAC successfully connects to another computer with the same OS, try copying the drivers from a working system: