I have DS-7716NI-K4 NVR, used to work fine and for past few months keep receiving live camera failed and also playback issues. when trying any browser.
NVR has latest firmware V4.74.200 build 230522
Hi Dan the cameras I have are DS-2CD2385G1-I with firmware V5.6.820 build 220519.
All equipment was bought from a reputable trade only supplying company so no ambiguity of it being grey market.
It looks like the NVR & cameras are running the latest firmware and if you are not aware of changing any settings before the issues started then I can only think that there is possibly a fault with either the NVR or cameras.
We would recommend taking the issue to your trade supplier for their technical team to investigate and possibly arrange a warranty return/replacement.