TH refused point blank to eat Skinners Puppy Food, even though that was what the breeder fed her and like you I ended up with a full bag! She survived on puppy milk for a bit, with the odd mouthfull of puppy crunchies.
We then tried James Wellbeloved to the same effect. Finally she settled on Eukanuba puppy and junior for large breeds which she is still eating 15 months later. This comes with a feeding guide depending on the age and weight of the dog, but the advice line will tell you to watch out for the end product and if he'she is producing more that 2/3 lots of poo a day, then they tell you to cut down the amount fed.
Their advice line was very helpful.
0808 100 70 30
http://www.eukanuba.co.uk/