My AG Belgian Dubbel will not carbonate! (HELP!)

I brewed a 7-Gal batch of belgian dubbel back in mid-Janaury and for some reason it did not carbonate properly (way under carbed).

I did a 90-min mash and a 90-boil and hit all my intended gravities.
OG: 1.062
FG: 1.013

I did two non-standard things that may or may not be a factor in the process:
a) I mixed both a Wyeast mini-starter and White Labs tube of Belgian Yeast strains together in my 2L starter (the mini-starter pack was old and expiring); and
b) After 2-weeks in primary, I racked to a secondary and kept in there for 5-more weeks @ 66F (controlled).

For priming I used 5.87oz of corn sugar to carbonate per the Beer Smith calculations and let it carb room temp for several weeks all in 22-oz bomber bottles. They all taste FLAT....

About 2 weeks ago I shook all the bottles up and let them sit for a while in hopes I might rouse the yeast, but still no change in carb level.

What do you think happened here?

What can I do to fix this? The beer is good tasting, just too sweet and flat.

Should I try and re-innoculate each bottle with yeast (dry or liquid)?

Any other options here?

Any help is greatly appreciated!

JW

That's odd. I'd guess either your yeast were unhealthy (did you oxygenate?) or too many of them fell out of solution in the secondary. Although that shouldn't be near high enough alcohol to negatively affect a Belgian yeast. And that isn't really a long secondary.

What yeast specifically did you use? Were they super flocculant?

If after several weeks they're as flat as America's job growth, I'd pitch a pack of Nottingham that I keep handy in case of emergencies.

I used the shake method for oxygenation, but since I made my target FG I figured the yeast were healthy.

Yes, the Secondary got extended way beyond planned. Life gets in the way of brewing..

I used Belgian Abbey Wyeast Propagator 1214 and WLP530 Abbey Ale, both were mixed into a 2L starter (intermittent shaking).

So what can I do to turn my 3 cases of overly flat and sweet 22-oz bombers of this Belgian Dubbel in to the beer it aspires to be??

Has anyone ever added dry yeast to bottles (after the fact) and then re-capped them?

Thoughts and Suggestions are appreciated.

JW