[Sephiroth]

That’s one of those messages with potentially complex causes. It boils down to one thing: During initial ranging, when it sets up the channels, there is one or more channels that are not performing well and no amount of power can drive intelligible signals through.

The cause of this could be noise on the circuit, cables not screwed in tight - anything that impairs signal travel.

Btw, you also have DOCSIS 3.1 channels, one each for downstream & upstream.