You supplied very little information.
Has the MH been plugged in over the winter?
Was the battery left "connected" in order for the converter/charger to be able to charge it?
Have you checked the battery(s) cells for correct water level? After adding water you may have to charge the batteries with a separate portable battery-charger until the voltage reaches at least 12.0 volts. From that point the converter/charger should be able to work after you "connect" the battery(s) to the circuit with the "disconnect" switch. If it connects you should hear a click from the solenoid and see a red LED lit on the control panel. The battery should charge from the converter/charger then.
Check the voltage with a multi-meter at the battery-terminals. The voltage should move from the 12.0 volt level up to 13.8 volts (14.4 + volts with multi-stage charger) in a short time. Charging to "full" could take 12 to 24 hours. The voltage will read 12.7 volts (over-night after disconnecting) if they can be fully charged.
If the converter/charger does not reach at least 13.8 volts it may have failed and need replacing. The battery(s) may also need replacing if left in a discharged state over the winter.