If you encounter this error message make sure that:
1) If you are using a dedicated cloud / on premise server, make sure the server url that is set in your test script is in the following format: https://<org>eyesapi.applitools.com. (see this article on how to set the server URL for your cloud / server instance).
2) If you are running on the public cloud, and are not setting the server url in your tests (as the public cloud is the default setting for this property), make sure you are running on the latest SDK version.