I want to set the update to a stable version of Fedora distro after I follow an system upgrade.

I try to follow this https://fedoraproject.org/wiki/DNF_system_upgrade
This not work well, the output comes with fc30, fc31, fc32 versions for packages and loop into this way, see the example:
...
Public key for zvbi-0.2.35-9.fc31.x86_64.rpm is not installed. Failing package is: zvbi-0.2.35-9.fc31.x86_64
 GPG Keys are configured as: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-30-x86_64
The downloaded packages were saved in cache until the next successful transaction.
You can remove cached packages by executing 'dnf clean packages'.
Error: GPG check FAILED
Any help with this issue?
mythcat