Have you tried swapping over the AC Adaptors? These are interchangeable between the two units.
Try this referring to the following “Establishing Power Supply to your Monitor” information:
Establishing Power Supply to your Monitor.
It is important to establish which component is at fault if you are experiencing a loss of power to your monitor. Please try the following:
• Remove all Batteries from the Nursery Unit
• Switch the AC Adaptors between the units, these are interchangeable between both units
If mains power is now established the green power light on the Nursery Unit will illuminate