I am working on a CCTV system for a farm.  The single LAN has a wireless link from the main house with the WAN connection and router, the link goes to a cowshed with an unmanaged switch which connects a Dahua NVR, and multiple cameras.  All the cameras at the cowshed connect through the switch (none directly), and they all work.  Back at the house I have onw camera connected to the main router, and it is visible on the NVR.  Also at the house I have wifi, and at a close by shed, there is a Nanostation M5 set in client mode and attached to the network.  It works fine, I can connect my laptop and get and IP and internet connection, and I can ping the NVR.  IF I connect a camera at this location it does NOT work.  If I connect the same camera at the cowshed switch, or to the house router, it does work and gets seen by the NVR.  When connected in the shed, it can be pinged on the same IP address that it gets at the other two locations... but the NVR cannot see it.

I have ruled out POE and cables as a cause, and I know the camera config works in one location and can see no reason it shouldn't work in another.

Any troubleshooting suggestions or ideas about possible causes, i'd love to hear them