My Ronin has decided to stop working although there is still power in the system as I am using the ptap output to power a monitor I can hear a faint sound of a motor but no connection with the app and no torque in the motors any thoughts or suggestions would be great
Regards

Hello!
Here is another relevant thread in our Forum for your reference: http://forum.dji.com/thread-2854-1-1.html
It's a little hard to figure out the issue only based on your above limited information, could you please give us more details?
If it's necessary, please contact your dealer or our after-sales specialist for repair.