q-codes have been designed to work with a range of phones and scanning apps. Most scan apps work best when the camera is square with the code and positioned so the q-code fills the active portion of the screen. Try moving the phone closer or farther away from the code until the scan is successful. Changing the angle slightly to avoid reflections may help as well. If you regularly have trouble scanning q-codes, you may want to consider a different app, such as one of the ones suggested above.