My NUC6i3SYB Bluetooth missing from Device Manager, do know from when it miss. BT driver that I installed is BT_19.00.1621_64_Win8.1.exe
In this case, we recommend a clean installation of the drivers. In order to do so, you need to remove the current drivers completely before downloading the latest driver. Here is how you can do it:
1. Download and save the latest version for this adapter: https://downloadcenter.intel.com/download/26172/Intel-PROSet-Wireless-Software-and-Drivers-for-Windo... Intel® PROSet/Wireless Software and Drivers for Windows 8.1*. Package version: 19.1.0 - The driver version for this adapter will be the 184.108.40.206
2. Then, once you have saved the drivers, do the following: go to Control Panel, Programs and Features and Uninstall the current "Intel® PROSet/Wireless Software", if it is installed. When prompted, choose the option to "Discard settings".
3. In Control Panel, Device Manager, Network Adapters, right click on the Intel® Dual Band Wireless-AC 8260 and Uninstall it. Make sure you mark the option to "Delete the driver software for this device".
4. Reboot the PC or scan for hardware changes, check device manager and if an older driver is detected and installed, repeat the actions to uninstall and delete it as well. Repeat this process until the OS does not allow deleting the driver, or until the controller shows as Unknown Device.
5. Install the Intel® Wireless driver. During the first steps of PROSet/Wireless installation, make sure to customize the installation and install all the 3 driver components.
Let us know if this procedure helped you.
Thank you for confirming that this situation has been resolved. Please, should you have any further questions or doubts, do not hesitate to contact us in the future.