sudo apt remove --purge xl2tpd
wget http://archive.ubuntu.com/ubuntu/pool/universe/x/xl2tpd/xl2tpd_1.3.12-1.1_amd64.deb
sudo dpkg -i xl2tpd\_1.3.12-1.1\_amd64.deb
sudo apt install network-manager-l2tp network-manager-l2tp-gnome
sudo service xl2tpd stop
sudo reboot
This worked for me a few days ago but in the middle of the day today it stopped. Has the same happened to you?