Essentially the same thing. However, some mirrors go offline or stop syncing entirely. Check repo.manjaro.org for the status of the mirror you’re using.
I don’t know what method you’re using for this, but you should either be using a reliable mirror, or regularly refreshing your mirror list.
Mirror lists will only be automatically updated on an update of the
pacman-mirrors package, and only if you haven’t disabled that in
/etc/pacman-mirrors.conf. PGP signatures will only be updated on an update of
If you have a mirror that has synced extra or community but not core then you can end up with packages signed by an unknown key, and no update to either keyring package. This is one potential reason for the issue you first posted in this thread.
Regarding the second issue you posted, if things work sometimes, or they didn’t work before but do now, this is more than likely because the particular mirror you were using was out-of-date. This may or may not be a partially-synced mirror.
There isn’t only one, isolated, reason why packages show a key error that can be fixed with a single command or change to the current infrastructure or process.