The RF-coax connectors were on the right side when viewed from the back and there were two of them - one above the other if I recall correctly. I think I had the Cable connected to the top one, which I thought was labelled "TV". The input to the box was coax, not Cat5. I believe this was the PVR, not a STB, but I could be wrong since I'm not very familiar with Fibe
It's certainly possible I had the wrong output, but at least I solved it using composite/analogue audio and an RF modulator, which he had in his setup already - that's the way Bell had connected it (don't know why), but we were trying to also hook up a VCR/DVD recorder...
I managed to do that, but there were several workarounds that I had to utilize to make everything work with his very old equipment. (I connected composite/analogue audio to the VCR/DVD and then from the VCR/DVD to the modulator, then to the TV). It means he has to have the VCR/DVD on to watch Fibe, but he was fine with that since Bell could not get that to work and the VCR/DVD was useless to him until I got it working. He also wanted to record fibe, which my setup gave him, so he's happy.
The other weird thing was that the RF-coax output on the back of the VCR/DVD was only a "passthrough" and didn't send any signals to the TV when playing a DVD for example. The operating manual stated that and I tried it too, but it didn't work for watching a DVD, hence the need for the modulator in the loop.
Final resolution Fibe PVR -> VCR/DVD -> RF-Modulator -> TV