If this is the module.
https://www.dfrobot.com/wiki/index.p...o_SKU:_DFR0009
Then i would test the buttons with a sample program first.
The voltage on an analog pin changes as you press the buttons. I had 30 or so of them (no name brand but the same shield) and they all read the voltages differently.
Most of them were within spec but on some the values were off so the code did not work and the threshold values needed to be adjusted.