My home office is at the end of a 15-20m ethernet cable that a friend ran 15 years ago, and it recently stopped working. I tested it with a cheap continuity tester, hoping to discover a fault near one end, or that there were still 4 good conductors that I could reuse.
To my surprise, the cable tester shows continuity on all 8 wires, and no shorts. I've tried wiggling the ends of the cable while watching the tester, and even replaced one of the crimps where the insulation stopped short of the plug in case the lack of strain relief had cause a break.
I'm pretty sure the problem is the cable but can't prove it. I've tried swapping cables at the router, and the problem follows the cable, not the router port. Also my office machine works when connected via powerline ethernet (although that's a little unreliable, so I don't want to stick with it). I can't think of anything else that could be causing a problem.
Is there anything else I can do, or do I have to replace the cable? It's not terribly expensive, there's just a lot of stuff to move to get to it!