Bottles didn't carbonate, anything I can do?

I've had a similar issue with a brew. I just shook the crap out of it and 2 weeks later it was carbonated.

The better solution would be to add some more priming sugar though.

A heads up for future use :) When doing natural carbonation, storages temperature is extremely important. That is, the amount of sugar needed to achieve adequate carbonation depend heavily on the temperature you plan to store your beer at..

Assuming you're aiming for an average carbonation level of 2.4 vol co2 AND you plan to store your beer at room temp (i.e. 72F / 22C) you'll need: 0,22 oz/L or 6,4 g/L.

If you're aiming for the same carbonation-level but storing your beer at around 50F / 10C (which I often am) you'll need 0,17/L oz or 4,8 g/L..

If you are sure your primed the bottles then they should most definitely carbonate. It could be a temperature issue creating sluggish yeast. What temperature are your bottles at? Get them to 70F or better and they'll start carbonating. Put one on top of your water heater for a few days and see what happens.

EDIT: You know another great place to warm bottles is on top of the fridge. The fridge generates a fair amount of heat in the back, and it generally is escaping from the top. I have put a case of bottles on top of the fridge before and trapped the escaping warmth with a towel or small blanket. Alot of fridges have those two hard to get to cabinets above the fridge. I 'll put a case on top and them use the doors to hold the towel to make a tent over the bottles. This helps trap that warm air around the case of beer. Of course if you have a super nice kitchen and a wife this might not fly very well.

A last resort is to use dry ice as you serve it. Cools and carbonates at the same time. Used to rescue flat soda this way (poor chemistry students, you know ;-)) and I have used it on hard cider to improve the carbonation while serving. Dry ice can be found in most large chain supermarkets these days.

IMPO I wouldn't do anything. I have have some batches that have taken 5 weeks to carbonate. You mentioned that the last time you tried them they didn't taste as flat as the first time, which would indicate that they are carbing up, just slowly. Good call on rotating them and putting at a little higher temp. This should get them going, just have patience. I would not under any circumstance add more sugar. It sounds like you primed them right and if you add more sugars you could end up with bombs.

I had the same issue with an oatmeal stout. I also used 4oz of sugar. It ended up okay in the end though after turning the bottles upside down, gently rousing the yeast and raising the temperature. Not familiar with that yeast strain, but I'd imagine 64 is too low for the yeast to be happy. Raise the temp, swirl the bottles upside down and give it a couple more weeks.