No carbonation in bottle after six weeks -- what to do?

Have to ask: What yeast did you use and HOW did you prepare it? How much and how healthy was it prior to being pitched?

Wyeast Scottish ale. I made a step up starter that was full of white chunks. Lots and lots of cells.

I had to use a blow off tube and it still seemed like it could explode. That went on for almost 3 days.

Could be the cells are not able to thrive in the higher alcohol environment to eat the priming sugar?

I calculated the abv to be around 8.5 or 9 with the sugar. Wyeast website says it can tolerate 12.

This summer I'm going to really get them warm and see if that helps. If not I'll eventually keg.

It sounds to me like the possibly you have leaky caps?

That could be as well. Have you ever had problems with capping prior? Is this a new or different capping routine / supplies.

It's not the caps. I've bottled hundreds of beers (which is why I have kegs now) with no issues. I've had beers take 1.5 to 2 months but never this long.

I've only been into this hobby for 4 months. I've bottled 12 batches and have only encountered a flat beer with my imperial IPA. I have the sediment on the bottom of the bottle (I assume the DANSTAR BRY-97 Amerocan West Coast yeast and nothing more) and I can see it get kicked up when I swirl. I have bottled other beers that are carbonated, but this batch won't carb up.

I am going to rehydrate Red Star Champagne yeast tonight and pitch into my Imperial Stout. I'm hoping the yeast won't eat too much simple sugars in the secondary and only chow down on the priming sugar for bottling and priming.