The battery may be dead and the handset will need to be on the cradle for a while in order to charge. If the battery is not holding a charge or dying often, please clean the metal contacts where the phone meets the receiver.
If there is power on the handset but it doesn't seem to be working, try rebooting the handset (not the phone). Please follow the below steps to accomplish this:
Press and hold the larger button on the handset
There will be a quick beep, but keep holding until there is a chime.
Wait a few seconds and then repeat to turn the handset back on.
The handset can then be set in the cradle and within a few seconds, it will reconnect to the phone.