Happy Day! I am picking my boys up from college, so I have emptied out my enclosed trailer and I am ready to go....except my GX550 keeps telling me the "Brake Controller is Off". I don't see how to turn it on...the manual slide does nothing... the plus (+) button to turn up the gain does nothing but give me the OFF message? (Truck acknowledged theirs a trailer connected, lights all work....I went into the menu and told the car it's 0-4999#) Any hints, tips or suggestions?