Got the firmware from Andy, here's a link to it in my Dropbox:
Dropbox - General_NVR5XXX-4K_Eng_V3.210.0003.0.R.20170418.bin
It's way past my bedtime. I had no luck trying to upgrade the firmware through the NVR webpage. Ended up putting it on a USB, plugging it into the front of the NVR, and upgrading from there.
I don't use the NVR directly a lot, so I'm not sure if this is really new (vs. something I didn't notice before), but you can zoom/focus the 5231 varifocal from the right-click menu now. That's cool.
Also haven't had chance to play around with this at all, but the Smart Play option from the main menu now shows IVS and Vehicle Recognition. Before, mine only showed Facial Recognition.
Andy recommended that the NVR be set back to defaults after the firmware update is done. I'll do this tomorrow, don't want to mess with it tonight.