TLDR; A computer and monitor works at site A, but the exact same setup fails at site B - the only difference is the power sockets used.
I have a HDMI over ethernet box which allows me to use Cat6 cable to carry a video feed to a remote monitor.
At site A, I connected the below components, and it worked.
Desktop PC > HDMI cable > HDMI Sender > Cat6 cable > HDMI Reciever > HDMI to VGA cable > Monitor.
The PC, Sender, Reciever and Monitor are powered with UK plugs.
However, if I move the exact same components to site B, the system does not work (no monitor output).
Site B has several other systems working OK (computers, monitors etc..), and has never had any power related problems before. The PC works fine at Site B, and detects that it has a monitor connected. The Monitor works at site B when plugged in directly.
Is it plausible that the building's power at Site B is faulty in a way that allows everything to work excepting these HDMI to IP extender boxes?