In the case that your controller is connected to your PS4, but the connection seems to be off. Then it's recommended to delete the connection and re-pair the controller to the PS4 console. This can be done as follows:
- Disconnect the controller from the console
- Go into the settings of your console and delete the Bleutooth connection between the PS4 and the Guitar controller
- Now restart the console (make sure the PS4 is completely turned off)
- Turn the PS4 on and reconnect the controller back to your PS4, make sure the guitar controller has sufficient battery power on the console. You now will be ready to go!