I installed Cadabra in fedora 27 using the version given in https://cadabra.science/packages/fedora26/ . However when I click to start, the window disappears within milliseconds.
Can anyone help me.
Not entirely surprising; there is absolutely no reason why a package built for Fedora 26 would work on Fedora 27 as the library versions on these two distros are not the same. I'll try to add a Fedora 27 to the build farm but it may take a few days.