Hi Steve,
As Mark has pointed out, the current stable version of LibRaw does not provide complete support for the Nikon Z7. Please be patient. The RAW module is a critical component of PixInsight's preprocessing pipelines, and I cannot release it based on an unstable version of a support library, such as a snapshot of the LibRaw library. As soon as the LibRaw team release a new stable version, I'll release an update of our RAW module for all platforms, which hopefully will support the newest camera models.