+1 re the advice from NewsHound. Metal is bad.
My first deployment of a sensor was on my garage door. The V2 cam with the bridge was in the kitchen, at the rear of the house. The distance between the two was too great. No sensing whatsoever.
I relocated the camera to the dining room, which is at the front of the house, adjacent to the attached garage. Bridge-sensor separation about 10 feet, through the common wall between garage and house interior. Wall construction is plaster & lath on the interior, cement parging over particle board on the garage side. with blown cellulose insulation in between. (All those materials will attenuate the RF transmitted by the sensor).
At first, I thought it was working OK, but after putting it into service, the sensor function was unreliable. My garage door is the really old kind with a pair of counterweights (one on each side of the door) comprising big steel cylinders full of concrete that go up and down. When the door is closed, the counterweight rises up, and was right next to where I had mounted the sensor on the side of the door near the top. And right next to the sensor, blocking the radio waves from the sensor to the bridge. Doh!
I relocated the sensor and the magnet to the top of the door, away from the counterweight. Although the distance between sensor and bridge is now a bit longer, the operation is more reliable.
The operating range of the bridge is really quite limited.
Metal in the way - bad. Intervening walls - bad.