I would guess that the toggle interrupts current from the roof mounted panel and the auxiliary input from the exterior mounted module. This may have been installed so that the combination of both modules does not overcome the capacity of the solar controller.
As was posted, you will need to measure the voltage at the output wires of the solar controller to see if power is being delivered to the batteries. For this (and other sundry electrical items), you will need an inexpensive meter and learn how to use it.