What is the prerequisite before a Single-VM Blueprint in Self-Service (formerly Calm) can be published...

Before a Single-VM Blueprint in Self-Service (formerly Calm) can be published to the Marketplace, it is necessary to create both a project and an environment. A project defines the scope and access control for the blueprint, while the environment provides the necessary configurations and settings for the deployment, such as network, credentials, and other resources.

References:

Nutanix Calm documentation on Project Creation.

Nutanix Calm documentation on Environment Setup.