We are baffled by your question. How could you let a vanilla bean dry out? Surely you weren’t saving it and saving it and saving it for a special occasion? Yes, they are expensive, but not that expensive.
A vanilla bean should stay potent for four or more years. Was yours exposed to heat? We honestly have not come across your problem before. If the beans are still fragrant, you could use them to make vanilla sugar, by storing the beans in your sugar container. The sugar is delicious in sweet baking products. If they’re not fragrant, they’re probably not worth keeping.
Our only other suggestions, and they’re just guesses, is to steam a pod briefly in a vegetable steamer, or pop one into the microwave for 8 to 10 seconds, to see if either method makes them more supple.