One possibility is that the area you are fermenting in is simply not warm enough. My ginger bug wasn't really doing much after five days when I started him recently, so I covered him with a towel (to protect him from direct light) and put him on our warm back deck. He was thriving in a couple of days.  Another possibility is that the ginger root was irradiated or rinsed in something that killed the beneficial yeast and bacteria. That should not be the case with organic ginger, but it may happen from time to time. If placing it in a warmer spot (as mentioned above) doesn't work, I'd assume it is the ginger and start with a fresh piece.