Server API call failing with: class NotASignedMessage error

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(imported topic written by GreenEagleLeader)

Attempting to make a Server API call (version 8.2.1372) to create an action using the besimportfile-1.2.exe program and the steps found in this article:

https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/Tivoli%20Endpoint%20Manager/page/BigFix%20Platform%20API

Upon executing the call, the following error is returned:

BESAPI.XMLImporter.ImportFile error: class NotASignedMessage

This occurs whether using a master or non-master operator and whether running the Server API on the server or on a console machine.

Any ideas what might be wrong?