Were they at 17 during fermentation or did they reach a significantly higher point?
A very quick calculation (that I may have stuffed up) suggests that your rate is around about 90g for a 20 L batch. This will give quite low carbonation and if your beer has been cold at all during carbonation time or if your beer reached warm temps for a while during fermentation, this low carb could easily be little/no carb in the time frame you suggest (less than two weeks).
Bring a couple inside, put them in a warm water bath and test them in a week. If they are no better, then think about opening and re-priming. If they are better, even if not perfect, then wait and try and keep the rest at 18-20 consistently.