Default [Q] EPCTEK 5200mah Power Pack

Hello,

I bought an EPCTEK 5200mah battery power pack from eBay. The reviews on Amazon were good so I was quite positive about it, but I seem to be having some problems and I just wondered if anyone knew how to make it work right. When I press the ON button, it lights up but then it goes off straight away. It's as if it doesn't know the phone is there.

This is the battery pack in question:

http://www.ebay.co.uk/itm/1711209337...%3AMEBIDX%3AIT