This happened to me too, I had to re-install fedora. The only thing I could see as the problem, was that the first time I didn’t run dnf upgrade after the installation, but first I installed another repos/plugins/packages. The second time, I first run dnf upgrade, reboot and keep installing other stuff.
Also, if you are seeing timeouts when installing a gnome extension, maybe this could help Failed to synchronize cache for repo 'fedora-modular'