1
Open the Settings App.
Go to System - Troubleshoot
Click 'Other Troubleshooters'
Run the Bluetooth troubleshooter from the resulting page
Check if Bluetooth is then working
2
If not, open Device Manager (accessible by right clicking your Start Button)
At the top of Device Manager, choose View - Show Hidden Devices
Does that show hidden Bluetooth device(s)
If so, right click and uninstall that
Restart your PC
Check if Bluetooth is then working
3
If Bluetooth is still not working, go to the support page for your PC on the manufacturers website, then from there, download and install the Bluetooth device drivers they recommend.