@Tcfd 

Hello, please check the troubleshooting suggestions below:

https://www.tp-link.com/support/faq/2316/  (Q7)

1. Make sure your Bluetooth device is set to be discoverable.

2. Please unplug the UB400 and reinsert it. Or you can also disable it in the Device Manager and enable it again.

3. The device that was once paired cannot be scanned again unless you delete it. So please try the following steps on your PC before another scan:

Go to Control Panel > Hardware and Sound > Devices and Printers, and then you will find the devices that was previously connected to your UB400/UB4A on the Devices page. Right click on that device and select Remove device. And then try to scan one more time on UB400/UB4A and you will be able to find the device.

4. For the devices with non-standard Bluetooth protocols, there may be some compatibility problems. Please refer to Q8 to check out the compatibility list.