The error typically occurs when a build server (like Azure DevOps or GitHub Actions) cannot access the external Octopus Deploy repository to retrieve the required Octopus CLI tool . This is often due to strict firewall rules, network outages, or misconfigured "just-in-time" installation tasks in your CI/CD pipeline. Core Causes of the Failure
For self-hosted agents, the system expects the CLI to be pre-installed as a "capability," but it is either missing or not in the system's environment path. The error typically occurs when a build server
Change the version field in the Octopus CLI Installer task from * to a specific version like 9.1.7 . Change the version field in the Octopus CLI
The pipeline task is set to fetch the latest version, but it fails to communicate with the update server to determine what "latest" is. Manually install it once on the server: Older
If your agents are behind a restricted firewall, do not rely on the pipeline to download the tool at runtime. Manually install it once on the server:
Older versions of certain build tasks require specific .NET versions (like .NET Core 2.1 or 5.0) to run the auto-downloader; if these are missing, the download fails silently or with this error. Step-by-Step Troubleshooting 1. Pin a Specific CLI Version
OctopusDeploy/cli: | Public | Next Generation of the Octopus CLI