I'm also getting the 'Sorry - this isn't available' message every few minutes.
Download speed is 112.02 Mbps
Last week I was getting the 'Maximum of devices reached' message when I tried to watch TV. On Saturday I called the VM Helpline and they deleted all my registered devices. Now I don't Sign Out of the TV Go App and all seems well.
There are lots of people complaining about TV Go showing this unhelpful message across all channels. It is a regular occurrence for me - for several hours every day or two. It would be nice if someone from Virgin Media would explain what it means and how to fix it.