Possible cause:The network between the SIP server and the IP phone is unavailable. Specifically, VLAN or 802.1x parameters are incorrectly set on the IP phone.
solution:
Set VLAN or 802.1x parameters correctly on the IP phone.
eSpace 7800 series
On the phone screen, choose Menu >Settings > Advanced Settings > Network, and set related parameters.
eSpace 7900 series
On the phone login screen, choose More >Network > Network Access, and set related parameters.
