Hello,
I gather you didn’t update in quite some time. Run this commands from TTY if you can’t do it from Terminal:
sudo rm -R /etc/pacman.d/gnupg/
sudo rm -R /root/.gnupg/
sudo pacman-mirrors -f5
sudo pacman -Syy gnupg archlinux-keyring manjaro-keyring
sudo pacman-key --init && pacman-key --populate archlinux manjaro
sudo pacman-key --refresh-keys
sudo pacman -Syyu