The purchase option is disabled. What’s going on?
The Nucleus models have reached their end-of-life, and are no longer available. The Titan has been announced and apparently may be launched next month. It’s possible that further models will be added to flesh out the range, but this is pure conjecture on my part.
You might find a dealer that still has one. I suspect, but don’t know, that Roon is coming out with an updated Nucleus at a lower price point than the Nucleus Titan.