I can't tell from the screenshot, but did the other packages install successfully? I can't read the language of the output, but with something like a failed install, I might try a couple of things:
- Reboot the machine
- Force a reinstall of the flatpak in question (org.gnome.Platform) (IIRC, it would be
flatpak install --reinstall org.gnome.Platform) from here.
- If it's a TLS issue, some Internet searching looks like it might be an issue with the machine clock being incorrect to the actual time. Maybe update your system clock? Are you using Budgie or Gnome?
Hopefully something in that is helpful. If not, maybe a little more information could help us figure out how to help.
