Replace the adapter. A modern USB Bluetooth 5.0 dongle (e.g., TP-Link UB500, ASUS BT500) costs $10–15 and works instantly with Windows 10 native drivers. If it is an internal card, you can disable the ISSCBTA device in Device Manager and use an external dongle.
Download the last official ISSC driver from your PC manufacturer’s support page (e.g., Acer, Asus) for Windows 8.1 (64-bit). Install it using compatibility mode: isscbta driver windows 10
If your Windows 10 system shows a "Bluetooth USB Host Controller" or an "Unknown Device" in Device Manager, follow these steps to install the driver: Method 1: Automatic Update (Recommended) your ISSCBTA Bluetooth adapter. Right-click the Start button and select Device Manager . Replace the adapter