The operating range is 330 meters/1000 feet outdoors and up to 50 meters/150 feet indoors. The operating range of the Philips Avent Baby monitor varies depending on the surroundings that cause interference.
Place the units next to each other and test again. If this works, we advise you to decrease the range between the baby unit and parent unit.
If this did not solve the issue, please contact us for further assistance.