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I found this for the CSR Bluetooth USB Adaptor that worked in Win 7 and then didn't when I upgraded (??) to Win 10 - Uninstall the CSR Driver...

Under windows 10 there's no additional Bluetooth software/driver needed to use a USB Bluetooth adapter. You can use the internal Microsoft Bluetooth stack. After plugging in the Bluetooth USB adapter it is integrated automaticlly. So please uninstall any Bluetooth software you've already installed on your system once more and replug the USB stick. Then reboot the system. After replugging, the USB stick is integrated automatically with the built in Microsoft driver. To make sure, that the adapter is using the internal Microsoft Bluetooth protocol stack, please go to the system's device manager and find out, if there are the following entries listed under the Bluetooth listing. -Generic Bluetooth Radio -Microsoft Bluetooth Enumerator If there's still an entry like "CSR…., Rightclick this CSR entry and update the driver for the internal Microsoft driver. Please note: Some missing Bluetooth drivers are being updated automatically by the windows update.

I un-installed the CSR Driver that worked in Window 7 & checked in Device manager that all CSR related devices were un-unstalled, restarted & then inserted the Bluetooth adaptor into the PC.
A device found notification popped up, new Microsoft driver installed and the Bluetooth is back!
Image result for windows 10 csr bluetooth driver site:answers.microsoft.com

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