Bourbon Barrel Porter 1 Gallon Beer Recipe Kit

I haven't actually brewed this one yet. Authentic Havana Club rum from Cuba will be used instead of bourbon when I brew this one. I've got a batch of Holiday Red ale conditioning right now. It smelled delicious after fermentation.

Good easy making beer! Taste great

First time with a NB kit and the instructions are clear and simple to follow. Brew day had an OG of 1068, 7 days in the fermentor then added my oak cubes and bourbon and left for another 7 days (sat at 1015 for 5 for those days). Added the correct amount of priming sugar for a porter style and left them for 2 weeks before sampling, on opening there was some carbonation but far less than expected (had one at 3 weeks and no difference).
Overall a tasty beer but the lower amount of carbonation and head retention did slightly ruin the enjoyment of it.

Why is it so flat? Taste is fine but it's like an old soft drink in a 2 litre bottle that's 2 weeks old. Can I expect this if I do a 1 gallon Stout also? The citrus IPA was excellent. What happened and how can I fix next time? Thanks!

My husband loved making this and had really high hopes but once the bottle conditioning was complete, the beer was flat. He could barely hear any sign of carbonation when popping the tops off the bottles and refused to even try it