I upgraded my Fedora 24 machine to Fedora 26 using the dnf utility, copied the disk to an SSD and then put the SSD into a new laptop. It worked well, except that there was no sound when I had finished. I traced this to pulseaudio not starting. To disgnose the problem, run pulseaudio in verbose mode. It showed that the sound card was different in the new machine. fix the problem, remove the pulse directory and restart :-
rm -rf ~/.config/pulse