Session disconnected

I'm running a Windows 8.1 machine with the companion application installed. As a test I managed to connect to the machine fine from an external network, connect, login, worked like a charm. As this worked fine I didn't check it again and went on holiday expecting to be able to log in just as I had done before. However as mentioned in the title I just get 'session disconnected' every time I try to connect to my home PC.

Nothing has changed on the home PC. I can see no reason why I am unable to connect with the machine now when I could just a few days ago. I'm using pocketcloud pro on my tablet. And whatever the latest version is on my home PC. I can't see how my PC is now not working or letting the connection through when it worked before with no issue the first time.

Any ideas?