I would suggest the following recovery activity:
sudo rm -r /etc/pacman.d/gnupg
sudo pacman -Scc
sudo pacman-mirrors --country all --api --protocols all
sudo pacman -Syy gnupg archlinux-keyring manjaro-keyring
sudo pacman-key --init
sudo pacman-key --populate archlinux manjaro
sudo pacman-key --refresh-keys
sudo pacman -Syu
Afterwards, reboot.