Thanks for the tip. That was the problem (the missing file diagnostic_logs/device_info.xml).
I'm surprised more people don't have this problem, since the instructions at the wiki here -
https://wiki.mobileread.com/wiki/Kind...king#Jailbreak as well as the readme file do not mention copying the diagnostic_logs/device_info.xml file from the kindle-jailbreak-k4-1.6.N jailbreak directory.
Thanks again!