Ohhhh. Okay. I see.
So the bare end of a wire is in contact with a touchscreen, and the opposite end is connected to the primary contact on a relay which connects to a positive power supply, and when the relay closes, the charge sent down the wire is supposed to simulate a finger touching the screen in that area?
I don't know too much about touchscreens but is it possible that the newer touchscreen is programmed to reject anything that is too different from the conductivity or charge of a human finger? Maybe try adjusting the positive voltage you are using? Or reverse the polarity?
Does it work any better if YOU are the one physically holding the opposite end of the wire rather than it being connected to a power supply?'
EDIT: I tried this using a a piece of metal to swipe my phone:
1. If I am touching the piece of metal, I can use it to swipe.
2. If I recently touched the piece of metal but then hold it with an insulator, I can still use it to swipe.
3. If I continue to hold the piece of metal with an insulator but then drain the charge from it (by touching it to the screw on a lightswitch on the wall), I cannot swipe with it until I physically touch it again with my skin.
Unfortunately I don't have a battery handy so I can't do something like applying a charge to the piece of metal that isn't my own to see if it still works, or if the phone ignores it because the charge is too different from my finger. You might want to try that on your end (or just mess around with the voltages on your setup).