I was trying to use a Bluetooth device on Windows 10 running in Parallels on a Macbook Pro, but without luck.
Parallels can share its Bluetooth connectivity, but it’s not very reliable.
The solution is to get a Bluetooth USB dongle, and being a Macbook Pro, I also had to get a USB C to USB A adaptor.
I found the Plugable USB-BT4LE USB Bluetooth 4.0 Low Energy Micro Adapter with a Ailun Type C Adapter worked.
Before you plug in the dongle, you need to go into Parallels and stop sharing built in Bluetooth device to your Windows 10 instance.
Now plug the dongle in. You will need to assign the USB device to Windows 10 in Parallels when prompted.
Windows 10 will complain that the device doesn’t work. To fix this download the Windows 10 drivers. Once installed you need to restart Windows 10, but after you do Windows 10 will have a working Bluetooth connection.
Parallels has a habit of sharing the built in Bluetooth service when you restart, so make sure this is disabled if you are having problems.