batteryProtect 12/24V 65A blijft in error E3 hangen

Vitron batteryProtect 65A after switch off power and back on, BP gifs error E3 (under voltage) on BP 14V (also on battery) battery is a LiFePO4

how to reset the E3 and what is the correct setting for the liFePro 12,8V

update; E3 is gone. now I get E1! nothing is changed! what can be the cause?