Question about Avantek Radio bell

Plug in the receiver, press the volume button for approx. 3 seconds until the light lights up red, then press the button on the transmitter (remove the plastic tab in the housing by the button cell beforehand!) and it should ring.
Otherwise I don't know what to do.

The transmitter (bell button) is supplied with a plastic tab that insulates the battery. This tab must be removed from the transmitter once. Otherwise see below. LG

Normally it works by itself, but some houses have a Faraday cage and don't let the waves through. Try connecting the transmitter and receiver in the same room and see if it works.