Replacing ZA3N with ZA3P red led flahing

[Bluefastcar]

I am replacing a lightening destroyed ZA3N with a ZA3P (couldn't get a ZA3N anymore). I am getting the Red programming LED flashing, but no action. I have shorted the movement sensors which did not help. Do I perhaps need to put some shorting links in the limit switch connector? I have dual gates with ATI motors. I have read the manual multiple times, but not getting anywhere. I would have expected a simple(!) panel swap to be straightforward.....
Any help gratefully received.