Anyone ever had any trouble with 1028 and carbonation?

I brewed a batch of Christmas Ale using 1028 and after a month in the bottle (@66 - 68 degrees) there is no more carbonation than the day it was bottled. Gravity shows the sugar is not being consumed.

Anyone ever had any trouble with this yeast? I dont use it much, only for this brew. Ive never had the problem before.

I opened a couple of them and pitched some dry yeast and then recapped, hopefully that will take care of it.

I know this is really basic but are you absolutely 100% positive you added the priming sugar? The only time I had zero carb at a month, this is what I obviously did. Felt pretty stupid and I'm still not sure how it happened, but it did.