Install libnm-glib-vpn1 by entering the following commands in the terminal:
sudo apt update sudo apt install libnm-glib-vpn1
network management framework (GLib VPN shared library)
NetworkManager is a system network service that manages your network devices and connections, attempting to keep active network connectivity when available. It manages ethernet, WiFi, mobile broadband (WWAN), and PPPoE devices, and provides VPN integration with a variety of different VPN services. . This package provides the shared library that applications can use for creating VPN connections via NetworkManager.