I bought this tone generator: allsun Automotive Short Circuit Tester Finder Cable Tester Wire Tracker Detector Tone Generator EM415PRO https://amzn.eu/d/bTFyJJz
All trim and kick-plates are off but carpet is still down on passenger side. Traces all the way from the load area to the female plug under the driver's seat IF it's UNPLUGGED.
Tone can be detected all the way from the load area to the door on both wires... I assumed all the soaking in Contact Cleaner and cycling if the plug had fixed it.
I vote the car front to back not left to right like JLR So FR is Front Right and FL is Front Left. The crossovers say woofer so I use W in the codes but call the speakers bass.
To eliminate the FR crossover I connected the FLW wires to the currently vacant FRW terminals: Sound from FL bass driver.
To eliminate the FR bass speaker (again) I connected it into the FL door: Sound from FL bass driver.
Left FR bass in FL door because there's no point switching it back when I know both of them work.
Switched FL bass wires back to FL crossover. Tested and still working.
So, I now have GR/BL and BL/GR wires for FR which pass the test tone all the way from the load area to the door and a known working speaker from the FL door.
Fitted and connected FL bass to FR door, reconnected GR/BL and BL/GR wires to the (now) known good FR crossover.
Silence. Nothing. Nada. Null point.
That is an odd one...
Have you tried the continuity test with your multimeter from the loadspace to the connector?
The only other thing I can think of (without it being in front of me to poke and prod at myself) is that when it plugs in there's a high resistance, which stops the tone. Out of interest, have you tried reading from the loadspace connector to the door connector with resistance (on ohms on the multimeter, rather than continuity check). The continuity checker on my multimeter goes up to maybe 200? ohms resistance - so anything over that, if there IS a connection, but it's high resistance, then it won't read anything - but if you click it to say the 2K ohm range, you don't get the continuity beep, but you can see if there's a resistance along the wire.
Might be something else to look into, in case there is a problem in that connector...