The information you provided is not sufficient to provide a definitive answer, ideally, including the code for the page that handles the callback and the Auth0.js configuration and call to
renewAuth would allow to troubleshoot this better.
However, you mention that it works when you switch versions so there’s one thing to have in mind; version 8.6.1 included a fix for an issue introduced with version 8.6.0 related to this functionality. Please ensure that you don’t use version 8.6.0 neither in the callback page nor in the main application (it’s not likely that you do because 8.6.1 was released just a few hours after it) but nevertheless it’s something worth checking. If the problem persists do update your question with more information to troubleshoot.