Still not able to register the phone but I think I made progress?
New SEP config I am using is below, as soon as I updated it to this I saw that the phone started to request two new files from me that it wasn’t able to find: lk-sip.jar and g4-tones.xml.
I found what may or may not be a completely incorrect version of those files here: Index of /Cisco/IOS/IP Phones/7942G/English but am pretty skeptical because it doesn’t explicitly say these files are for 99XX variants…
When I added these files to the TFTP directory, the phone got them and then it looked like it rebooted, then just showed me the home screen again with “Phone not registered” on it. Status page of the phone now says “VPN Error: VPN not configured” so not sure what that is about yet.
I also found an interesting post from a long time ago here: Cisco 9971 phone configuration working example with setup tips - #47 by troy_orndoff
This person seemed to have the same problem I am encountering but said that you can get more info by accessing the web server on the phone (which for some reason I am still unable to do even when trying to include the setup in my SEP config).
<device>
<deviceProtocol>SIP</deviceProtocol>
<loadInformation>sip9951.9-3-2-10</loadInformation>
<devicePool>
<dateTimeSetting>
<dateTemplate>D/M/Y</dateTemplate>
<timeZone>GMT</timeZone>
</dateTimeSetting>
<callManagerGroup>
<members>
<member priority="0">
<callManager>
<ports>
<sipPort>5060</sipPort>
</ports>
<processNodeName>192.168.20.44</processNodeName>
</callManager>
</member>
</members>
</callManagerGroup>
</devicePool>
<sipProfile>
<sipProxies>
<backupProxy></backupProxy>
<backupProxyPort></backupProxyPort>
<emergencyProxy></emergencyProxy>
<emergencyProxyPort></emergencyProxyPort>
<outboundProxy></outboundProxy>
<outboundProxyPort></outboundProxyPort>
<registerWithProxy>true</registerWithProxy>
</sipProxies>
<sipLines>
<line button="1">
<featureID>9</featureID>
<featureLabel>Room</featureLabel>
<proxy>192.168.20.44</proxy>
<port>5060</port>
<name>1</name> <!-- extension -->
<displayName>Room</displayName>
<authName>1</authName>
<authPassword>pass</authPassword>
<messagesNumber>*97</messagesNumber>
</line>
</sipLines>
<preferredCodec>g711ulaw</preferredCodec>
<natEnabled>false</natEnabled>
<phoneLabel>Room</phoneLabel>
<userInfo>1</userInfo>
</sipProfile>
</device>