Your Transfer Switch is automatic and is where I showed you in the picture. When the Genny is turned on it will pick up the relays in that box after 30 seconds delay. There is no switch to throw by hand. Take off the cover and rap the relays with a piece of wood. After a few years they get residual magnetism and don't pick up. Same as folks use to find in pinball machine relays and solenoids. Be very careful inside that box, as it switches the "Deadly Shipmate 115VAC". If rapping on them WITH WOOD doesn't help then you will probably need a new box. They cost around $150 and should be installed by a pro to avoid any potential fire hazards.
1999 Tradewinds 7372 Cat 3126