Hi, there are some problems to install from “Fedora Linux (RPM)” in Software
failed to parse public key for /var/cache/PackageKit/36/metadata/google-cloud-cli-36-x86_64/yum-key.gpg
Also in Updates tab it showes old date.
Note: it works fine using dnf tool from terminal, to upgrade and install applications.
The error message shows that google-cloud-cli is the problem. That’s a dnf repository, you can see it in dnf repolist. You probably added it when installing GCP CLI. I ran into a similar issue and solved it by disabling the repo with dnf config-manager --set-disabled ${repo}. You can also try moving the file elsewhere from /etc/yum.repos.d. Means you can’t get updates from that repo though
Hmm, try also removing/renaming (ie change its extension to .bak) the file under /etc/yum.repos.d and then rebooting and checking updates again. That worked for me at least, if that doesn’t work then I can’t help further
After disabling the broken repository, you might need to refresh the PackageKit cache, perhaps?
pkcon refresh force
Not sure what exactly helps, but I have renamed to google-cloud-sdk.repo.DEPRECATE, after that did
pkcon refresh force
and
sudo dnf upgrade --refresh
And now I can install my favorite clementine 
I had the same problem, pkcon refresh force worked.