2 batches taste flat

my first batch has been in bottle for about 3 1/2 week, and it taste flat, when i open the bottles(espesially the ones in swingtops) it makes a nice pop like its been carbonated well,b but still tastes flat.

my second batch has been bottled for almost 3 weeks and i tried one, and when i pop the cap there is very little sound from the carbonation, and its completly flat, no bubble in the beer...

i used john palmers method for priming both batches, and now i have a 3rd batch to bottle and i dont know what to do..

Keep them at 21C until they are carbonated, even if that is a couple of more weeks. How much priming sugar did you use, and what type?

You just need more patience. If a beer isn't ready at three weeks, there's nothing wrong.

The 3 weeks at 70 degrees, that that we recommend is the minimum time it takes for average gravity beers to carbonate and condition. Higher grav beers take longer.

Stouts and porters have taken me between 6 and 8 weeks to carb up..I have a 1.090 Belgian strong that took three months to carb up.

Temp and gravity are the two factors that contribute to the time it takes to carb beer. But if a beer's not ready yet, or seems low carbed, and you added the right amount of sugar to it, then it's not stalled, it's just not time yet.

Everything you need to know about carbing and conditioning, can be found here Of Patience and Bottle Conditioning. With emphasis on the word, "patience."

If a beer isn't carbed by "x number of weeks" you just have to give them ore time. If you added your sugar, then the beer will carb up eventually, it's really a foolroof process. All beers will carb up eventually. A lot of new brewers think they have to "troubleshoot" a bottling issue, when there really is none, the beer knows how to carb itself. In fact if you run beersmiths carbing calculator, some lower grav beers don't even require additional sugar to reach their minimum level of carbonation. Just time.