Phoenix 12/250 Low Battery Alarm

Good day,
I have a Phoenix 12/250 that i a client brought to us not switching on a at all. Upon inspection, i realized that the switch is broken and replaced it. The only issue i have now is, the inverters shows all the normal parameters in the victronConnect app and multimeter, AC out and battery voltage looks proper, but as soon as you connect load on it, The output voltage becomes 0 and a battery low alarm but the battery voltage is above 13V. What could be the cause of this? The inverter settings are on default. Already tried downgrading the firmware but it did not solve the problem.