Flat beer

Hi All,
I've brewed two batches of IPA and added 3oz of priming sugar diluted in some water . These batches were stored in King Kegs. Both were flat (No conditioning) with no head when tried a month later. At first I thought that the valve was leaking and in one keg this was so because when I fitted a new lid to the keg for my next batch it was full of life but after fitting a new lid/valve to the other and giving it a 2sec burst of gas it only trickled out 2hrs later although there was no gas escaping. Could this be that this batch is knackered although still drinkable or maybe not enough priming sugar?
Thanks in advance
Kevin

How much sugar for how much beer? I had a similar problem and I used the proper amount of sugar with nothing after 4 then 6 weeks. I then took some advice and placed a few grains of dried yeast into the bottles an voila, carbonation! One bottle was even a gueser!! Give it a try, it won't affect the flavor since it's such a small amount.

I added 3oz (imperial) per 40 pints (Imperial)