try these steps from M$ help forum, i had issues with BT as well, but i dont recall what fixed it
Settings > Devices > Bluetooth & other devices . Make sure Bluetooth is turned on.
Make sure your device is turned on, is charged or has fresh batteries
Make sure airplane mode is off: Select the
Start button, then select Settings > Network & Internet > Airplane mode . Under Airplane mode, make sure the toggle is turned off. Try turning Bluetooth on and off: Select Start button, then select Settings > Devices > Bluetooth & other devices . Turn off Bluetooth, wait a few seconds, then turn it back on. Remove the Bluetooth device, then add it again: Select the Start button, then select Settings > Devices > Bluetooth & other devices .. Under Bluetooth, select the device you’re having problems connecting to, and then select Remove device > Yes. To learn more about how to add your Bluetooth device again, see
Connect a Bluetooth device
Settings > Update & Security > Troubleshoot . Under Find and fix other problems, select Bluetooth, and then select Run the troubleshooter and follow the instructions.