I took my AGM 31 series battery to be checked at an auto parts store and its reading 12.7 volts, which is suppose to be a good battery ?? The reason for my checking is that my display on my level up does not read. When hitting the on/off button the center green light does come on, but when I go to hit other buttons for re level or ECT. the display does not light up. Can someone help me please ?? Thank you