Upgrading Elastic-Agent with source-uri failing


I'm attempting to upgrade Elastic-Agent 8.0.0 (tar.gz installed) to 8.2.2 via the command found in the documentation:

elastic-agent upgrade 8.2.2 --source-uri https://URL/elastic-agent-8.2.2-linux-x86_64.tar.gz

This is failing with

Error: Failed trigger upgrade of daemon: cannot be upgraded; perform upgrading using Fleet

I can CURL the tar.gz just fine from the server.

This is an air-gapped environment so I must be able to use a URL here. Is there a more detailed error I'm missing here? I put the agent up to debug logging but saw nothing logged when running the upgrade command.