Power Tailgate not opening

[solorider]

I have a 2010 ST elite, the tailgate will not open under power, if you press the button the tailgate will start to open then it shuts itself and there is 3 beeps, it closes ok though, I have just replaced the power strut and pump with a second hand unit as before I had nothing at all.
Anyone have any ideas

[solorider]

I get at least 6 beeps