i bottled a batch that barely carbonated for 6 weeks. so, i turned each bottle upside down, and gave them a shake to rouse the yeast at the bottom of each bottle. the beer was fully carbonated 2 weeks later.
Tap: Centennial IPA (SMASH)
Tap: Dogfish Head Ginger Saison
Bottle: Stone 11th Anniversary Black IPA clone
Secondary: Flemish Brown Sour Ale
I got that on my Whiskely ale. It took 9 weeks & 6 days to condition,then 2 weeks in the fridge before it got good carbonation & a 2 finger head. It's not just the gravity,it's how intense the malt profile is. Big beers can take a while to condition,so be patient,it'll get there in a couple of months.