Are you still on the stock ECU? If the car originally had EPS then it’s likely the ECU would not have provisions for hydraulic steering. A quick google search shows that pin 16 (green/black) should be correct, but I’m not 100% sure if you should be using logic ground or power ground (probably doesn’t really matter) but you could always try to ground the black wire right to the chassis and see if that works. If it doesn’t then explore the different ECU options that are available (i.e. find an ECU that comes from a PS equipped car). Good luck and make sure you post the solution if you ever find one.