I had issues with my TVGo. When I logged in it was showing I had used all 5 devices.
Clicking on the http://manage-virgintvgo.virginmedia.com/skydevices using Chrome (Version 83.0.4103.106 ) kept resulting in the message took too long to respond.
I opened the browser in a new incognito window and lo and behold, the screen tells me you can now register up to 6 devices and make 3 changes a month.
Happy news we can now have 6 devices.
It's a pity the app can't recognise you are using the same device but a different browser as that would solve the issue of using too many devices