I had same problem. use package in this page (or build it if you don't trust) http://tomtomtom.org/networkmanager-openconnect/
On Ubuntu 16.04 the network-manager-openconnect and network-manager-openconnect-gnome plugins are not usable because they are to old to use with the current version of network-manager.
This is the english version of this guide from a german ubuntu support forum.
Unofficial built packages are available here:
NOTE: You wonxc2xb4t get any security updates for this! It is just a workaround until the packages will have been fixed in the official repository!
Using VPN is a security feature - so it is better to build the package manually from source because you donxc2xb4t know what I put into the packages. :-P
At first remove the unusable packages
sudo apt-get purge network-manager-openconnect network-manager-openconnect-gnome
You will need the build-dependencies.
sudo apt-get build-dep network-manager-openconnect
(NOTE: For this the 'deb-src'-Sources in /etc/apt/sources.list must be active.)
You can do this with sed e.g.
sudo sed -i s/#deb-src/deb-src/g /etc/apt/sources.list
the new dependency for the new version.
sudo apt-get install libnm-dev
and the sourcecode from GNOME project.
Unpack the tarball
tar -xf NetworkManager-openconnect-1.1.93.tar.xz
change to the unpacked directory
and run the configure script.
./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var --libexecdir=/usr/lib/NetworkManager/ --enable-more-warnings=yes --disable-static
start compiling .
and install manually
sudo make install
install the dependency for use the software
sudo apt-get install openconnect
or build a package with checkinstall
If you do so enter this:
networkmanager-openconnect as package name
adduser, libc6, libdbus-glib-1-2, libglib2.0-0, libnm-glib-vpn1, libnm-util2, network-manager, openconnect as requirements
If you get errormessages by installing the package try
sudo apt-get -f install
to resolve unmet dependencies.
To use the software it is necessary to add a systemuser for this
sudo adduser --system --quiet --home /var/lib/NetworkManager --no-create-home --gecos "NetworkManager OpenConnect plugin" --group nm-openconnect}
At last restart the system.