Sometimes when you bottle the gelatin knocks a lot of the yeast into the bottom of the fermenter, so you don't get much into the bottling bucket. You can put maybe a quarter packet of fresh US-05 yeast into the bottling bucket when you add the corn sugar charge to ensure there is plenty of healthy yeast for a 3-4 week bottle conditioning time. Also the fresh new yeast will assist removing the residual oxygen from the bottle, helping to keep the beer fresh longer.
I had a similar batch which would not carb up. At about the 2 month point, I added some US-05 to some distilled water in an 8 ounce Mason jar. Using a sanitized eye dropper, I carefully uncapped one bottle, squirted some yeast solution into the beer and quickly recapped. Uncap them one at a time and recap, do not leave them all open. Worked like a charm!