I(using windows machine) have been using Teamviewer recently. I had to help a friend who lives in Italy, so I told him to install Teamviewer for Ubuntu on his laptop.He did everything and told me his client ID so that I could connect to him , but after I press the start session button the Teamviwer software says "Could not establish a connection. Reason unknown." I have used teamviewer to connect to my own mobile and friend's PCs in my own country and it works perfectly.Also my friend in Italy can connect to my PC using the teamviewer software. What are the reasons for thhis issue and possible workarounds ?