I have two yuccas gifted to me that were big but young when planted and took 3 years to shoot a stalk (both). Some folks love 'em, others hate them. They reminded me of home so I was happy to take the offering.
At the old family house the Yuccas were planted at the base of a tree. I tried to dig some prior to the gift plants and it was impossible between their root systems and that of the tree. They resembled your pictured "dead" yucca briefly thereafter but returned. Also, in the course of 20-some years where the huge, impenetrable clump of healthy yuccas simply failed to send stalks and bloom.
If they're not in the way and potentially desirable to you I'd wait it out a while. Yuccas aren't an area of any expertise other than having cohabitated with them.
