Pumpkin beers tend to take between 6-8 weeks to carb when above 70 degrees. The three weeks we talks about is JUST THE MINIMUM for average grav beers. Beers can, and often do take longer.
Remember, carbing is nearly foolproof. You add sugar the yeast will carb the beer, at exactly the right length of time that it needs, and not a moment longer.
There are very few true carbonation issue in brewing, the majority of them are simply patience ones.
That's why I always find it funny when folks try to "over think" or "over diagnose" carb problems "did you stir or didn't you?" stuff like that. The reality is, if they added sugar in 99.9% of the time, the beer will carb, eventually.