This is an upstream report of downstream Fedora bug https://bugzilla.redhat.com/show_bug.cgi?id=2011333 . As reported there, if you go to Settings and toggle a repository from enabled to disabled or vice versa, the operation does actually happen, but the checkbox is not redrawn until you leave the Settings tab, go somewhere else, and come back. This is very confusing and could lead users not to know what repositories are actually enabled after trying to change the states.
*** This bug has been marked as a duplicate of bug 406295 ***