Cat 304 all hydraulic functions stop working. Engine runs. It will not start when the safety lever is down. That means the safety switch is probably working? When the safety lever is down/off there is no pressure in the joysticks like the pilots are not sending oil to the controls. Also, the auto idle does not work when you move the joystick (engine doesn’t rev up). I checked all the fuses under the seat. So there must be some other component that is telling the pilots not to send oil to the controls. Serial Number TTN00453 
Hello Sir one potential issue could be the pilot lock out solenoid which could be faulty or not energizing. Another possible problem is that there is no pilot pump pressure due to a fault with the pilot pump, its drive coupling assembly or the main pump drive coupling assembly. I have attached some info to help identify the solenoid and pump.