Your Cisco phone reads Offline. This sometimes happens suddenly after weeks or months of working properly.
- Power-cycle the network (this will usually resolve the issue for phones that had previously been working properly).
- Change Ethernet cable.
- Use a different port or switch on the router.
- Try assigning a static IP address on the phone.
- Is the modem a combo device?*
- Yes: Place in bridge or pass-through mode.
- No: Continue to the next step.
- Check for and disable:*
- Restricted NAT
*If all Cisco phones in network are reading Offline.
The phone is unable to register with the SIP server.