You know that a week is hardly a lot of time at all, and yet you still started a thread about why it's not carbed?
You answered your own question!!!!!
The 3 weeks at 70 degrees
, 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.
If you just arbitrarily put them in the cold at three weeks, without making sure they were carbed to begin with, then you've prevented them from carbing further.
Yeast go to sleep in the cold, they don't carb your beer. SO of coulrse you beer is stuck uncarbed right where you put them into the fridge.
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."
Lazy Llama came up with a handy dandy chart to determine how long something takes in brewing, whether it's fermentation, carbonation, bottle conditioning....
Your cider fits into the high gravity category.
Walk away, for a long, long time......I've had hard ciders take 6 months to carb up.