However we couldn't figure out how to put it up - we've ended up deciding that there is a piece missing! It is a standard tunnel type with three arches. The arches are held in arch shape by a strap that runs underneath with a peg at each end which goes into the end of the pole.
2 of the above straps are in place but the 3rd is missing so we can't put it up

I take it I am right that there should be 3 straps? There isn't some fancy way of holding the 3rd pole in place is there?
We got the awning as part of the deal from the dealer, so haven't got a receipt as such for the awning. I have emailed the manufacturer via a contact form on their website (couldn't find a phone number).