This page contains a web-app that can record your voice, provide some analysis about how masculine or feminine it sounds and (if you choose to enable that) manage those recordings.
In order to be able to do so, it is necessary that you have javascript enabled and give this site the permission to access your microphone. If you decide against either or both of these things or if you don’t have a microphone, there is sadly not much it can do for you and this application will not work.
If you believe that you have done those things and are running a current browser, but the site still does not work, please file a bug-report. (Or contact Fiona on Fedi, if you don’t want to use gitlab.)