This is one of the "error messages" that says exactly what it means. You have low voltage to the system. You must determine what is the cause of the low voltage, bad/low battery, poor connections to either power or ground.
The level up works regardless of what position the disconnect switch is in, however the battery will not receive a charge if the switch is in the off position. (you can remove the key only in the off position)
Here is some very good information for you when having any problems with the level up system:
http://lci1.com/assets/content/suppo...ting_Guide.pdf
The battery/batteries must be in top condition to operate the hydraulic system as it has a high current draw. If you don't have two batteries I would recommend you add an additional battery.
Good luck