Zip Is Not a Supported Package Format?

[Octopus Deploy] ##teamcity[publishArtifacts ‘C:\TeamCity\buildAgent\temp\buildTmp\ZipPreprocessor7797053728239272864\’]
[17:46:22][Octopus Deploy] Octopus Deploy Command Line Tool, version 3.3.14+Branch.master.Sha.b29e34402b1a139ae52f9d53915811e7d1691a6f
[17:46:22][Octopus Deploy]
[17:46:22][Octopus Deploy] Handshaking with Octopus server:
[17:46:23][Octopus Deploy] Handshake successful. Octopus version: 3.3.12; API version: 3.0.0
[17:46:23][Octopus Deploy] Authenticated as: trustood <>
[17:46:23][Octopus Deploy] Pushing package: C:\TeamCity\buildAgent\temp\buildTmp\ZipPreprocessor7797053728239272864\…
[17:46:34][Octopus Deploy] Error from Octopus server (HTTP 400): There was a problem with your request.
[17:46:34][Octopus Deploy]
[17:46:34][Octopus Deploy] - The uploaded file isn’t in a supported package format.
[17:46:34][Octopus Deploy]
[17:46:34][Octopus Deploy] Exit code: -7
[17:46:34][Octopus Deploy] Octo.exe exit code: -7

Closing as duplicate of