Elite Zumo incorrect power

Hi, I have just replaced an elite novo smart after 2 1/2 years with an elite zumo. I’m having no end of issues getting it setup, the novo just worked as it should out of the box.
My issues are incorrect power reading compared to my 4iiii power meter, the zumo is around 30watts down at 200w. I’ve tried calibrating it using the elite app, it gives me a figure of around 16000, but still remains 30w down. I’m using Ant with Windows 10, the laptop picks up the trainer but for some reason the elite android app on my phone won’t pick up the elite power meter using ant, only Bluetooth. I don’t have Bluetooth on my laptop.
The other issue is ERG using zwift, the novo was rock solid at tracking the wattage, the zumo is all over the place, up and down, even with a smooth cadence. Both issues occur on Windows and android.
Can any one help?
Thanks.