Hi there Lindafos,
Firstly I'd like to welcome you to the forums and say that I'm really sorry to hear that you're experiencing some issue with your on Demand service at the moment, I'd really like to help you out.
I've run some testing on your set top box, and can see that there are some signal issues, so I'd like to arrange for a technician to call out and investigate further for you.
I've sent you a private message in order to get things sorted, please look to the top right of this page where you'll see a purple envelope icon, click on that and you'll see my message.
Many thanks and apologies once again.
Huw