This means that your display unit is not in range of your transmitter. The maximum range of the display unit is 30 meters and the signal can be detected through two walls. Try and situate your display unit closer to your transmitter. Other reasons that the signal strength may be very weak or lost may be:

• Radio interference: This is unlikely in a home environment but if this does occur, try moving the display unit away from any possible source of interference and check there is no source of interference close to the sensor. 

• The transmitter is located in a metal meter cabinet: the wireless connection between the transmitter and display unit will not always work through metal. 
  

If you have tried all the above and you still have no signal you may need to re-pair the display to the transmitter.