Victron Multiplus II

i am using Victron Multiplus II 48v 3000VA inverter, i am controlling using Modbus TCP with Cerbo GX to control, everything is working fine but the problem is that , like i am seting the power using set point, but the problem is that after around 1 minute the the power is set to around 600W regardless even if i set power 1000W or 1100W or value above 600W it stays constant.
does anyone know what might be problem ?