Nethunter on Nexus 7

Please forgive my ignorance but I am having an issue with Nethunter on my Nexus 7. I can't seem to apt update or apt upgrade; It seems the repos in sources are not available anymore and not only am I not sure which repository to add for Nethunter but I'm wondering how I can get this thing as current as possible and up to speed. Any help is greatly appreciated!!!
Model: Nexus 7
Android version: 5.1.1
Kernel version: 3.1.10-Bricked-v0.591-g0a2e5f6
Build #: LMY47V

It is running Lollipop but the download for Nexus 7 in the Nethunter downloads is for Marshmallow and it won't install (Not sure if compatibility there is an issue). I can save the Live Log from the Nexus Root Toolkit while trying to install if that will provide some insight but for me it is jibberish for the most part.