Agreed. I wondered where the reference to Sky boxes came from, but if you look at the responses I gave to the suggested 2 routes (1 via "Manage My Sky Devices", both of them ended up at the URL "http://manage-virgintvgo.virginmedia.com/tivo/" which doesn't work.
What network are you trying this on, home wifi or a corporate one? - Home wifi via a VM SuperHub 2AC
What Browser are you trying on and what operating system do you have - Google Chrome: 77.0.3865.120 (Official Build) (64-bit) OS: Windows 7 Pro 64bit SP1 (Build 7601.24544) - These are the same components which worked with 'Manage My TV' several months ago.
As an experiment, I backed off Chrome to version 76, which I just realised I was using the last time I used 'Manage My TV' successfully - Problem still seen. I have also just tried using Chrome 79.0.3945.130 - Problem still seen.