The voltmeter has a fixed measurement range from 0 to 100 VDC, the only switches on the board are for powering it on and a hold button, which freezes the value currently being shown in the three ...
This is a good place to use an old-fashioned incandescent test light. Using a voltmeter will not put load on the circuit. If the power side is good, then check that the bulb has a good ground.