Having had no luck accessing it on my phone (iphone 5 ios 9.2) I've tried on my laptop. I've tried all different combinations of my phone number including 07xx xxxxxxx, 07xxxxxxxxxx, +447xx xxxxxxx, +447xxxxxxxxx, 447xx xxxxxxx and 447xxxxxxxxxx and three different web browsers, Chrome, IE and Mozilla and I still can't access it.
Is there a further button you can click on? I've not needed to do this for a couple of years, but there's an extra step that's not intuitive, something like clicking on a check box next to the message when you've got the one you want to see displayed.
We have experienced exactly the same problem and similarly have been unable to access the video message. Our problem appears to be the tel no. By default the virgin number on the message starts with something we do not recognise, that is the number 447. When we try to clear it and enter our correct tel number we get an error message, when we add our tel number to 447 we get an error message again, not surprising as it makes it a long number! Like you we have been using both mobile and desk top but without success. So much for making things easy!
Forgive my ignorance! We managed it in the end. Hardly intuitive! Just knock off first two numbers of phone number and add in the three numbers given by virgin. Presumably some sort of international dialing prefix.