Thanks for getting in touch, I'm really sorry On Demand has been unavailable.
I've tried to run some tests on your V6 box but it's currently showing as offline from here. If it's switched off or in standby at the moment, could you let me know once it's powered on? If not, could you restart your Hub, wait for that to come back online and then restart the v6 using the power switch at the back of the box? Once you've done that, go to Home > Help and Settings > Settings > Network > Connect to the Virgin Media Service now and try On Demand again.
I'm sorry that you're still getting this error message.
Is this happening on just one programme in particular or all Catch Up and On Demand?
I've checked your account again and both the Hub and V6 are showing that they haven't been restarted for a while. Could you restart the Hub, wait for that to come back online and restart the V6 using the power switch at the back?