Inverex Inverter VM 2.2 problem

Hi Fellows, i am using inverex vm 2.2 but facing problem it not taking max power from PV.Its takes max 500watts.When load exceeds 500watt its start taking power from battry and when battry voltage drops it switch to utility.It should take max power of 1200watt from PV. I using 1800 watts PV panels on roof but this inverter not goes more than 500watts even i set angle of PV panels.
Suggest me any solution.

What does brochure/datasheet says?

You need to give more information, i.e. configuration of panels, output voltage and current from panels, solar intensity (bright noon sun or partly cloudy), etc.