I'm sorry that your On Demand is not working reliably right now for you. I have taken a look into this for you and it looks like it's due to some high demand going on in the network you're connected to.
This will mainly happen during peak times but can happen at various times of the day. The reference for this is: F003770024 and work is currently being carried out to make the necessary improvements. This work may take some times and the next review date is currently set for 23rd Dec 15. If the issue is still ongoing after this time don't hesitate to get back in touch and request an update.
I'm sorry for the inconvenience caused, we'll hopefully have this sorted for you soon.
All the best.
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