its possible the splitter is faulty but unlikely - same goes for any cables supplied
so start with just splitter and hub -
cable from wall box to spitter in - 2nd cable from splitter out to hub - if that does nor work try other outlet on splitter
post the upstream and downstream levels with and without the splitter as they will change and that could affect the connection
and post some photos of it all connected
log into hub3 - 192.168.0.1 [or 192.168.100.1 if in modem mode] - DON'T SIGN IN, click - click router status [centre of screen] - and post the downstream and upstream figures - to see those press on the grey buttons/boxes labelled - upstream - downstream
if its an earlier hub button is top right
you DO need to sign in on hub4
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Tony