If your scan returns a score of 0%, this doesn’t necessarily mean that Viper is not working correctly. Because of how Viper processes and scans your work, it’s possible for a 0% score to show even when there are small content matches such as references.
You may wish to try scanning your document again to verify that no plagiarism is found. Essentially, if a score of 0% is returned, your document contains virtually no plagiarised content.