If you haven’t tried, you can also use repair with --user or --system, depending on the installation, and possibly with sudo.
Another thing to try is to reinstall the problematic package. Logically, this should be flatpak install –reinstall package. Note: I’ve never tried this because I haven’t encountered such problem, it’s just one thing I found.
Contrary to what I said before, I think I had already had this checkback error (but a long time ago), and waiting did the trick. How long? I don’t know. Sorry, I don’t have any other possible solution.
Looking for updates… F: Warning: Treating remote fetch error as non-fatal since runtime/org.kde.kasts.Locale/x86_64/stable is already installed: No such ref ‘runtime/org.kde.kasts.Locale/x86_64/stable’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.kde.Platform/x86_64/6.9 is already installed: No such ref ‘runtime/org.kde.Platform/x86_64/6.9’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.kde.Platform/x86_64/5.15-24.08 is already installed: No such ref ‘runtime/org.kde.Platform/x86_64/5.15-24.08’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.kde.Platform.Locale/x86_64/6.9 is already installed: No such ref ‘runtime/org.kde.Platform.Locale/x86_64/6.9’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.kde.Platform.Locale/x86_64/5.15-24.08 is already installed: No such ref ‘runtime/org.kde.Platform.Locale/x86_64/5.15-24.08’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.gtk.Gtk3theme.Mint-Y-Dark-Blue/x86_64/3.22 is already installed: No such ref ‘runtime/org.gtk.Gtk3theme.Mint-Y-Dark-Blue/x86_64/3.22’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.gtk.Gtk3theme.Mint-Y-Dark-Aqua/x86_64/3.22 is already installed: No such ref ‘runtime/org.gtk.Gtk3theme.Mint-Y-Dark-Aqua/x86_64/3.22’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.gnome.Platform/x86_64/48 is already installed: No such ref ‘runtime/org.gnome.Platform/x86_64/48’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.gnome.Platform/x86_64/47 is already installed: No such ref ‘runtime/org.gnome.Platform/x86_64/47’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.gnome.Platform.Locale/x86_64/48 is already installed: No such ref ‘runtime/org.gnome.Platform.Locale/x86_64/48’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.gnome.Platform.Locale/x86_64/47 is already installed: No such ref ‘runtime/org.gnome.Platform.Locale/x86_64/47’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.freedesktop.Platform/x86_64/24.08 is already installed: No such ref ‘runtime/org.freedesktop.Platform/x86_64/24.08’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.freedesktop.Platform.openh264/x86_64/2.5.1 is already installed: No such ref ‘runtime/org.freedesktop.Platform.openh264/x86_64/2.5.1’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.freedesktop.Platform.ffmpeg-full/x86_64/24.08 is already installed: No such ref ‘runtime/org.freedesktop.Platform.ffmpeg-full/x86_64/24.08’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.freedesktop.Platform.Locale/x86_64/24.08 is already installed: No such ref ‘runtime/org.freedesktop.Platform.Locale/x86_64/24.08’ in remote flathub F: Warning: Treating remote fetch error as non-fatal since runtime/org.freedesktop.Platform.GL.default/x86_64/24.08extra is already installed: No such ref ‘runtime/org.freedesktop.Platform.GL.default/x86_64/24.08extra’ in remote flathub error: No such ref ‘runtime/org.freedesktop.Platform.GL.default/x86_64/24.08’ in remote flathub
I successfully installed the KDE runtime, version 6.9, from flathub. If the fetch error is true, it means there is a problem accessing the repository. Maybe a problem with a CDN? Did you change some settings in your network configuration? If not, only flathub maintainers can help you. Or wait until the problem is resolved if it is a server/CDN issue…