Can't install any flatpak software

When I download the file from flatpak official website it opens the ‘Software’ app, then, I click on the blue button ‘Install’ and I get this message:
After this, I tried to install it trough terminal with the command I found at the flatpak website: flatpak install flathub io.atom.Atom
But this gives me this message:

error: Nothing matches org.citra_emu.citra on remote flathub branch

I tried with atom as an example, tried couple of more software but get the same results

I had the same problem with another flathub app. I resolved with activating flathub repository

flatpak remote-add --if-not-exists flathub
1 Like