Recently I had cause to connect to my home VPN from my laptop, being out of town and on a connection not part of my usual trusted network. I tried to connect as usual using PPTP via the network manager on the Xubuntu desktop but no dice – the connection was failing every time. After establishing my iPhone was able to connect from the same network, I realised that the last time my laptop had successfully connected to the VPN was prior to my upgrade to Ubuntu 15.10 and therefore something must have changed with the default settings under the hood to cause the problem.
To cut a long story short, after much digging and hair pulling, I established that you need to enable 3 kernel modules to get the PPTP VPN client back up and running in the latest version of Ubuntu. Add the following to /etc/modules and reboot
After that you should find that your PPTP VPN connection invoked in the usual way from the network manager no longer fails. Happy days!