Used 7940 stuck on Protocol Application Invalid

[Callan hill]

I got this phone off a work friend because it wouldn’t work in his home network. When I bought a power cable and Ethernet and then powered it on it’s stuck in the Protocol Application Invalid screen and I do not own CUCM. I rely on the 3PCC Versions of the phones, so I have no idea how to fix this issue. Someone help?

[Maren Mahoney]

The Cisco 7940 phone does have an old firmware that allows it to run as a 3rd-party SIP endpoint (not 3PCC). However, the phone has been End of Life for so long, I doubt the firmware is available anywhere. If you don't have CUCM/CUCM Express or Asterisk (which can run SCCP phones) you may be out of luck.

Maren

[Callan hill]

So then how would I get rid of Protocol Application Invalid screen?

[Maren Mahoney]

Use the Settings menu to determine what firmware it is running in the off chance it's already running SIP (unlikely - the screen would say so). It is a bug and it seems a factory reset won't fix it.

I've not run into this issue myself, so I used "Teh Google" and came up with a few things....

https://community.cisco.com/t5/ip-telephony-and-phones/cisco-7940-protocol-application-invalid/td-p/2996580 

https://community.cisco.com/t5/ip-telephony-and-phones/7960-stuck-protocol-application-invalid/td-p/2096891 

https://community.cisco.com/t5/other-collaboration-subjects/cisco-7940-ip-phone-problem-protocol-application-invalid/td-p/584542 

You'll need to parse the docs to fit your own network and situation, but it does look like the phone is recoverable. Let us know if you have questions.

Maren