How good Qutext plagiarism checker is?

One of my clients today questioned me by showing me one of my content Qutext reports with a 52% copy score. The article was published 1 month ago. At the time of submission, I provided the report he asked for with a 100% plagiarism-free by using the tool he recommended then. Now 1 month later he is telling me that my content is copied and that's why it isn't indexed yet by checking it with Qutext. What can I do now?