Hi,
Same problem after same update ....
The connection with the NVR via the serial cable is ok, i found lot of tuto for cam but no for NVR.
I download firmware : DH_NVR5XXX-4KS2_MultiLang_V3.216.0000006.0.R.20190223 and unzip, so i have this file : PartionTable.bin, flash.bin, install.lua...