First Network Manager by default doesn't support L2TP, So first install network-manager-l2tp, Use below steps.
sudo apt install git intltool libtool network-manager-dev libnm-util-dev libnm-glib-dev libnm-glib-vpn-dev libnm-gtk-dev libnm-dev libnma-dev ppp-dev libdbus-glib-1-dev libsecret-1-dev libgtk-3-dev libglib2.0-dev xl2tpd strongswan libnss3-dev
Issue the following on the command-line (note: the backslash character \ is the shell line continuation character which can safely be copy and pasted):
git clone https://github.com/nm-l2tp/network-manager-l2tp.git
--disable-static --prefix=/usr \
--sysconfdir=/etc --libdir=/usr/lib/x86_64-linux-gnu \
sudo make install
Then try to match the encryption info with your windows system where it's working fine, If still doesn't work please post logs here.