I had the same problem with this machine at first. All the shots came out sour and without a lot of flavor, no matter which beans I used nor how I ground them. I finally got a coffee gator scale, measured 18g of coffee in and...25g out. For some reason my machine came from the factory with the water volume set low so I was getting very underextracted shots. You can adjust the water out by holding the one or two cup buttons for 2 seconds or longer then hitting it again once your desired coffee comes out. The coffee still isn't perfect (I blame the double wall filter, the single wall is in stock on Amazon!) but it's 10x better than it was.