"it turned and came out with just a modest psssst of co2."
You didn't have enough CO2 built up in the bottle. Champagne bottles and corks are designed to have a good amount of pressure inside the barrel. Without it, the cork will be VERY difficult to remove. I've had times where I've needed to cut the head off of the cork and use a wine opener to remove the cork.
If you were bottling regular cider, I would say you need to increase the amount of priming sugar. However, since you are keeving, this would mean you need to bottle the cider sooner. This way, before the yeast dies of lack of nutrients, it has a chance to create more CO2 while in the bottle. Do you know what the gravity was of the cider when you bottled last year?