Flat Beer?

I just finished a Belgian Dubbel and it is basically flat. This is now the second beer I've done with this problem. My first beer, however, (an IPA) had a perfect head. My Dubbel was in the primary for 10 days and in the secondary for 6 weeks. I tried the first beer 5 days after bottling and it was flat. I tried the second beer about 8 days after bottling - still flat. I know that I added the priming sugar to the bottling bucket. The only other thing I can think of is the no-rinse sanitizer. For my first beer - the IPA that carbonated properly, I used C-Brite. For the second two beers that turned out flat, I used iodophor. Could this be it? The recipe for the dubbel is below.

Thanks, E

EXTRACT KIT NORTHERN BREWER
Specialty Grains
0.25 lbs. Dingemans Caramunich
0.25 lbs. Dingemans Special B

Fermentables
6.3 lbs. Gold Malt Syrup
1 lbs. Golden Light Dry Malt Extract
1 lbs. Dark Belgian Candi Sugar

Boil Additions
1 oz. Spalt (60 min)
1 oz. Saaz (1 min)

Yeast
Wyeast #1214 Belgian Ale Yeast. Abbey-style top-fermenting yeast, suitable for high-gravity beers. Estery. Flocculation: medium. Apparent attenuation: 72-76%. Optimum temperature: 58-68.

Of course it's flat, it's only been 8 days in the bottle....

Read this and watch the video...

https://www.homebrewtalk.com/showthread.php?t=54362&page=11

3 weeks @ 70

3 weeks @ 70

3 weeks @ 70

Great information - thanks a lot.

E