Power supply for Zmodo wireless cameras?

A few years ago, I recommended a Zmodo system with NVR and wired 1080p cameras to a friend. A few months before the warranty expired, we discovered the repeater that powered the cameras had apparently failed. Zmodo was unable to replace it with another repeater, and instead sent a NVR sans hard drive to act in its place.

Now, months after the warranty expired, that appears to have also failed. Repeaters are difficult to find, and expensive if one does (even for used units). Likewise for NVRs that could act as a power supply and hub.

Is there any way to create a substitute? The page that lists the sPoE pinout appears to indicate that simply providing 19 volts DC on the proper pins won’t do the trick.

UPDATE:

To summarize, I discovered that if I disconnect the NVR (acting only as a power supply) from the network, the cameras can be recognized and even display on the video output on this diskless NVR. Shortly after I plug it back into the network, the camera(s) show as offline on the “Add Devices” screen, but will show online for a few seconds, before going offline again for about one minute and repeating that cycle.

Even when shown for those few seconds as online, they aren’t detected by the IP search in ZViewer.

Any clue as to why the NVR being connected to a network would cause the camera(s) to go offline?