Hello,
Even if you forgot device, its entry may remain intact in the database. So open Device Manager, click View > Show hidden devices. Locate your Bluetooth device, click Uninstall it. If confirmation prompt provides you option to delete device data, check it and proceed.
Reboot your machine and then try re-pairing your device by following these guidelines:
Ensure that your laptop has a Bluetooth adapter, whether built-in or an external Bluetooth dongle.
Make sure the Bluetooth function on the both devices to pair.
In the PC, right-click on the Bluetooth icon and select the option to add a new connection or device, which will make the computer search for available Bluetooth devices.
When another device appears, select it to connect/pair it to your laptop.
When prompted for a PIN code, try 0000 or 1234 and enter it on both the mobile device when prompted and your laptop. If this doesn't works, try searching for your Bluetooth device's manual online to find the Bluetooth code.
Hope this helps!