@Yoz Fair comment but I assumed you meant a direct connection using the supplied ethernet cable rather than an untested installed ethernet.
Those testers are cheap enough and will become a necessesity as speeds move on. Presently CAT5e is good for 1Gb up to 100 mts even for when Openreach upgrade to XGS-PON symmetrical (currently being trialled)..
@pippincp regardless of my own internal Ethernet being faulty in my scenario, I was trying to keep this out of the equation for simplicity, but I get without substance it may have seemed strange check to make if you've never seen it
I was simply trying to establish if the user was using powerline adapters as a patch at either end could have been faulty, or not have 4pairs connected in the cable, along with the sync speed between the powerlines. It was all a process of elimination. But I'm glad they got sorted.
Not sure if you are having the same problem I encountered @derekg30 . I was getting on average around 400 mb/s instead of the advertised 900 mb/s.
It took me a lot of research until I found it was my VPN that was actually throttling the speed. I turned it off and instantly started getting the correct speeds.
Hopefully, your issue is something as simple as this.
This is the problem i'm having. Was this ever solved? Horrible horrible speeds. Worse than normal copper based fibre