[cat0705]

Originally Posted by xxyzz

Don't download calibre from flathub, it's running in a sandbox and maybe that causes the error.

Run the command

sudo -v && wget -nv -O- https://download.calibre-ebook.com/linux-installer.sh | sudo sh /dev/stdin

to install calibre(see https://calibre-ebook.com/download_linux). All Linux users should use this command except Arch Linux users.

I reinstall calibre and it works perfectly now. Did not think flathub is the problem. Many thanks!