There are a few different circumstance that can result in this error message, so please start checking the following:
Make sure the PS4 controller is fully charged.
If controller lights up blue indicating it is connected to the PS4 console via Bluetooth, please follow the steps below to switch controller to USB connection.
Make sure you have the supplied micro-USB cable connected between the KeyMander 2 and the controller.
Turn off the controller.
Disconnect then reconnect the USB cable between the PS4 and KeyMander 2.
If controller lights up yellow indicating it is connected to the PS4 console via USB, but the KeyMander 2 still does not work properly, please check the following:
The keyboard, mouse and KeyMander 2 combination may require more power than available from the single PS4 USB port. Connect an additional cable from a USB power source such as a smartphone charger (minimum 1A) to the micro-USB port labeled “Power” on the KeyMander 2 and try again.
If that resolves the Question stop. If not, go to step 4.
If adding an additional power connection does not solve the Question, please follow the steps below:
Turn off both the console and controller.
Unplug the keyboard and mouse from KeyMander 2, but keep the PS4 controller connected.
Turn on the PS4 console using the power button on the PS4 front panel.
The PS4 controller should light up yellow indicating it is connected to the PS4 console via USB.