I'm an antenna installer, and it quite often occurs that all the TVs are suddenly not receiving a signal, but the antenna is intact. The most common reason I find is that antenna has an amplifier attached to it, which requires a power source, and most commonly this has been turned off, unplugged, or removed. It goes behind one of the TVs, and plugs into a TV point and needs a power point to plug into for the power. If it is missing, then you need to buy another, usually available from an antenna retailer, like Alvin or Laceys. ( I live in Melbourne).