The biggest thing to realize, and it's not hard, is that if you added priming sugar, and your beer is above the dormancy temp of the yeast, your beer will carb up when the time is right.
It really is a fool proof process.
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.
They blame insufficient mixing of priming solution (which I think is BS, just put the priming solution in the bottom of the bucket, and rack on top, it will mix thoroughly as the beer rises in the bucket,) or come up with all manner of complicated theories when there is only one simple answer.
If a beer isn't carbed by "x number of weeks" you just have to give them more time.
The yeast will eat the sugar, they will fart the co2, the co2 will build up in the beer and the headspace, and the co2 will saturate the solution and the beer will carb up. It's a closed system, it can't help but happen.
And the yeast HAS to eat the sugar, it is in it's DNA, the soul purpose for yeast's existence. It knows what to do, and RARELY will it fail you.
The 3 weeks at 70 degrees, that we recommend tends to be the minimum time it takes for average gravity beers to carbonate and condition. Higher grav beers take longer. Temp and gravity are the two factors that contribute to the time it takes to carb beer.
Using the 3 weeks at 70 as the "mean" an average grav beer at a temp below 70 may take a little longer than one above. Consequently, an average beer beer significantly above 70 may take less time to carb up. (I say may, because there is still a process that the beer has to go through to produce enough gas to carbonate the beer, and that takes time to generate no matter what temp it is at.)
Since the beer was at 65 degrees, though not a lot of temp range to us, may indeed be enough to add a week to the carb/conditioning cycle.
Also coopers drops tend to take a little longer that priming sugar solution anyway. So there's more time to add to the "3 weeks" right there.
Relax, it will carb up when it is time. I would move it to another place where the temps are above 70, giver them a shake to lift the yeast and come back to them in another 2-3 weeks.
