@avmad this NTL box (which was one of the companies which merged with enough to become Virgin Media - you really don’t want the hear the convoluted history), does it have two connections labeled TV and FM by any chance? If so it is the TV one you need to connect to - for reasons which are far too boring and technical and historical to go into now…
The older style connections were screw fit but the newer cables are push fit but are designed to be able to be ‘pushed’ onto the screw fit connector (no, no idea why they decided to change it, but whatever).