Did you put the beer in the fridge overnight before opening it? The problem you describe sounds a lot like bottled-carbonated beer that never had a chance to get the CO2 dissolved into the beer: lots of foaming when you pop the cap, then flat beer in the glass.
Gases dissolve more readily into cold liquid than warm liquid. When your residual yeast consumes your priming sugar, only a small portion of the CO2 it creates dissolves into your room-temperature beer. The rest accumulates in the headspace, building pressure. This is why most people will warn against natural carbonation in a growler - they're not designed to hold pressure, and the pressure generated can be much higher than pre-carbonated beer (yes, many people get away wtih it, but that debate is for another thread).
When you put your beer in the fridge overnight, the liquid cools down, the CO2 dissolves back into solution, and it doesn't spray all over the counter when you open it the next day.
You can check Denny's hypotheses by tasting the beer. Does it have off flavors, especially a sour tang? Too sweet? Taste like sausages?
Apologies if you knew this already - the question didn't specify.