If it hasn't sprouted in five months and there are feeder roots off it, that means either the eyes were damaged or (more likely) the tuber never had eyes to sprout from.

Toss it with no hesitation.

Thank you. Into the garbage it goes. Sad because it's a Cafe au lait and I've been wanting one in my garden. :(

Depending on where you got it, you could ask for a new one for spring. It's a bit late to expect a new one, but politeness, another order and the right customer service person might win you a shot at another without shelling out more cash for the same variety.