Flat

I bottled a batch and it's been sitting for two weeks, but still tastes flat. If you pour it violently it creates a decent foamy head, but still flat of course. What am I doing wrong? What can I do now that they're bottled? Would you ever suggest opening up the bottles and re-priming? Thanks in advance

Give it another few weeks. Two weeks is too early... sometimes WAY too early.

What style of beer is this? What's the OG and ABV of it?

My friend also had this issue, make sure to keep it around 70 just like fermentation process. I never had issues with bottle carbing. He has issues with some bottles being carbed and some not. It should only take 2 weeks to carb up. I do bottle carbing by added the cooled priming sugar at the bottom of the bucket before I add the wort. Also I gently stir the wort after about 5 or so filled bottles. Hope it carbs up for you.