Try downloading this free utility and see if it detects the keyboard.
BluetoothView is a small utility that runs in the background, and monitor the activity of Bluetooth devices around you. For each detected Bluetooth device, it displays the following information: Device Name, Bluetooth Address, Major Device Type, Minor Device Type, First Detection Time, Last Detection Time, and more.
BluetoothView can also notify you when a new Bluetooth device is detected, by displaying a balloon in your taskbar or by playing a small beep sound. BluetoothView