Make sure you select the proper playback device form the "Volume Control Options" by right-clicking on the Windows* Audio icon on the Taskbar*.
Additionally, you may try the latest audio drivers for your NUC for Windows* 10 x64 Intel® Download Center
This download record provides the Realtek* audio driver version 188.8.131.5281 for the front panel audio jack on Intel® NUC.
Audio output to a TV is provided by the Intel® High Definition Audio via the HDMI v1.4a interface and/or the DisplayPort 1.1a interface through the PCH which depends on the NUC model.
The Mini DisplayPort is compliant with the DisplayPort 1.2 specification.