IEE1901 adapter for connection of a network camera via koax

Not sure this is the correct forum, please move if necessary.

I wanted to help a colleague to install three network cameras atop his 
house. Unfortunately the only wiring in place is a sole spare koax meant 
for satellite distribution. So the idea was to use IEE1901 Adapters 
(more commonly known as PowerLan) on both ends and use a small switch to 
connect the cameras in the attic. The adapters came readily equipped 
with coax connectors and I used some  spare koax to rig up a test 
circuit in my basement first (DC power will be fed separately).

Funny thing was, I could run all my WAN traffic between modem and switch 
through the rig. But when I tried to use the same setup for the 
connection between a network camera and switch, the adapter on the 
camera side would not even show a „link established“ light.

What is going on here? Why would it work with high volume traffic but 
not with a single 2MP network camera? The camera was working flawlessly 
in my home network before, all IP addresses etc. are correct.

Any hint appreciated.