There are two buttons. One on the antenna itself and then the main power on the 12V outlet itself.
So find out where the TV plugs in. On the side of that plate (towards the outside wall) there is a little black button. That MUST be on to scan for over the air channels. That MUST be OFF to get cable.
PLEASE do not send questions via Private Message, my inbox fills up too quickly. Post questions in the forum as a new thread so that other users can benefit from the answers. Use Private Messages for sensitive information only (VIN, Contact info or things you do not want the public to see).