I have had a few sites where the ground relay test failed and finding the problem on a large installation is frankly a pain. I have made a video on why the test fails and posted that on YouTube with keywords "Victron Neutral Ground Relay Test". There are many reasons that would simply proof that you are an idiot so I ignored those reasons. The Neutral to Earth connection is mostly the difficult one to find in an existing electrical installation where one added a Victron system.
The problem is each time you isolate a circuit (read live and neutral) you have to switch the system off and start it again to see if the test fails. This takes an inordinate amount of time if you have many circuits.
If Victron can explain exactly how the test works, which impedance they test for, etc.. one can build a tester that would immediately find the error. I have seen in some cases (e.g.: light dimmers in one case) that simply testing between neutral and ground shows an open circuit. It's only when the live is powered that the Neutral to Ground leakage current exist.
Can Victron please help here?
I can see the sad result is that installers will simply not select the grid code to prevent the test from being done and have non-compliant installations, rather than spending days on site finding the problem.