If you have a problem with your Playstation 4 controller that it no longer works correctly and for example no longer connects to the PS4, the cause can usually be corrected as follows:
Resetting the Playstation 4 Controller - Instructions
First switch on the Playstation 4 completely. To reset the controller now, you need a needle, toothpick or narrow paper clip.
With this you must now press the reset button on the Playstation 4 Controller. The reset button is located in a small hole on the back of the controller, near the L2 button. Now press this reset button for approx. 2 seconds.
Connect the Playstation 4 Controller to your console with a USB cable. Switch on the PS4 afterwards. Now just press the PS button on the PS4 controller.
The controller should now establish a connection with the Playstation 4 and function as usual. If this is not the case, it is possible that your controller is defective and the warranty will be claimed.