Alla packages are downloaded, but when I get the following warning:
Errore: Il pacchetto libmpg123-1.22.4-1.fc24.x86_64.rpm non è firmato (unsigned)

but it is not installed
[root@pcdesktop1 antonio]# rpm -qa libmpg123-1.22.4-1.fc24.x86_64.rpm
[root@pcdesktop1 antonio]#

then
[root@pcdesktop1 antonio]# dnf system-upgrade reboot
Errore: system is not ready for upgrade