Hello Big dreams, did you peel the ginger? If you did, you removed the layer that contains the lactobacilli essential for fermentation. If you didn't peel it and it still didn't ferment, it likely wasn't kept warm enough for the duration.
To answer your question, I wouldn't give raw ginger root to chickens. It could make them quite sick (if you could get them to eat it). However, you could grate it very small, add just a tiny, teensy bit of finely grated ginger root to their food, and see how they do.
See, grated ginger root is used as an herbal medicine for treatment of Coccidiosis, and you'd use 1 tsp. in 2 gallons of water for sick birds. So if you weren't using it as a medicine, it would last a very, very long time!