“Auth Fail” message received when upgrading the firmware on a Cisco 7941/7961 phone.
While attempting to convert a couple of Cisco 7941G phones from the SCCP-8-5-4 to SIP, I encountered an “Auth Fail” message after performing a factory reset on the phone. The “Auth Fail” message was displayed while attempting to download the term41.default.loads file. If you haven’t reset the phone, you can encounter the error when the phone is attempting to download the SEP{mac}.cnf.xml file.
We use as Asterisk based distribution and attach Cisco station phones by converting from SCCP firmware to SIP firmware.
It turns out that the latest SCCP firmware is unable to authenticate the latest SIP image that I’m trying to install on the phone. In order to get past this, you’ll need to downgrade the phones current SCCP firmware to sip.8-5-2. After that, you can upgrade to the another version if you like.
Download “cmterm-7941_7961-sip.8-5-2.zip” from Cisco’s website. You’ll need a Cisco account to download the files, but the account is free. The steps to find the firmware appear below and are referenced from: http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/firmware/8_5_2/english/release/notes/7900_852.html
Step 1 
Go to the following URL: http://tools.cisco.com/support/downloads/pub/Redirect.x?mdfid=278875240
Step 2 Log in to the Tools and Resources Download Software page.
Step 3 Choose the IP Telephony folder by clicking +.
Step 4 Choose Call Control > Cisco Unified Communications Manager (CallManager).
Step 5 Choose your Cisco Unified Communications Manager version.
Unzip the 8-5-2 firmware into your tftp directory and overwrite the term41.default.loads and term61.default.loads. Reset the phone and it will load the term41.default.loads file. The term41.default.loads file will cause the phone to “upgrade” to the 8-5-2 firmware. When the phone reboots from the firmware update, it will load the SEP{mac}.cnf.xml. This is where you want to specify the firmware version that you’d like to end up with. This time, you won’t get the ”Auth Fail” error.
