need a bit more information
- is the charger turning on?
- insure you are plugging into the battery and not the forklift plug.
- use a vom meter and check the battery voltage before and after the charger is turned on to see if there is an increase in voltage after charger starts (if it starts up).

characteristics of what is happening when you plug into battery plug and turn on charger is needed to give an honest opinion of where to check