it could be the switch is in the wrong position or a wire is loose, or a fuse blown, or fuse missing.
the charger on ours tested across the battery terminals is 13.4 volts. with a multi meter set to volts
un hooked to electric ie turn the hook up lead socket in house off
the amount of energy in battery drops to its normal running voltage of perhaps 12.8volts dependant on time waited temperature, type of battery, or any drain ect
the battery power level wont drop if there is another power ie solar to recharge
hoping not said anything that you may already know