Check all the connections into the phone (5 Volt Power supply, RJ 45 Ethernet connection, and Handset cord.)
Check the Wall socket and confirm that AC power is available.? Try plugging another electrical device into the socket to confirm power.
If the phone is connected to the POE switch and not using the power adapter, make sure that the WAN port of the unit is properly connected to the POE switch and the link light on the switch is lit.? The Ethernet cable should be connected properly and known working.
Make sure that the handset cord is properly aligned at the bottom of the phone and connected on the handset port.
Check the registration status of the phone on the info tab of the SPA922 and make sure that it is registered.