Self Troubleshoot before proceed any further.
Please include the test result when resorting for email support.
1.Is "USB PnP Audio Device" seen by your Windows or Mac or is recognized as unknown device?
2.If it's recognized, is what you want to hear mic playthrough you computer speaker? (Please refer to monitoring part in the video below).
3.If computer sees it as unknown device, have you test out on a different computer? Tried to update and reinstall the unknown driver for a few times on the same computer?
Q: 1.the microphone is not recognized; 2.it is recognized but still no sound heard; 3.no sound on my Mac; 4.after upgraded from to Win10, the microphone doesn't work?
A: You can find step-by-step tutorial videos for above question on K668 problem-solving playlist: http://bit.ly/K669669Bproblemsolving
Q: How to use multiple K669/K669B microphones on one computer?A: Yes if you want to have a try, check out the link below. Basically, for Windows users, you just need to download an app called voice meter banana. If you use Mac, just create an aggregated device by using MIDI Audio setup.
Post: Using Multiple Microphones On One Computer
Q: Microphone doesn't work with my Skype!
A: 1.Follow the playlist: http://bit.ly/K669669Bproblemsolving to check if K669/K669B is working properly.
2.For Windows user, you can go to Setting→Privacy→Microphone, and set it to allow apps to access to microphone, at lasts restart computer.
3.Update Skype to latest version or re-install the latest Skype.