We recently discovered a bug in the v51 fleetcommand installer for Domino version 5.1.0. Using this installer will prevent environment builds from initiating. This will be fixed in the 5.2.0+ version of Domino but for now you can modify the nucleus network policy
cidr range during installation to be inclusive of the node IPs as well so that the host-based Docker image builder can access nucleus.
The suggested override is: