See if this works,
sudo pacman -Rdd networkmanager-fortisslvpn
garuda-update
sudo pacman -Rns $(pacman -Qtdq)
It seems networkmanager-fortisslvpn has been removed from extra repo in arch and it’s AUR versions have been marked orphaned.
Also, in case you still can’t boot using zen kernel try,
sudo dkms autoinstall
and,
sudo dracut-rebuild