Select the Start button, then select Settings > Devices > Bluetooth & other devices . Under Bluetooth, select the device, and then select Connect. Try unpairing, then re-pairing, the device. To unpair a device, select the Start button, then select Settings > Devices > Bluetooth & other devices .
: https://support.microsoft.com/en-us/help/14169/windows-10-fix-bluetooth-problems/

