"Connection could not be established" to Android devices (was working before)

itm60

I've been using Teamviewer on Windows 10 to control a couple of my Android tablets at home over the LAN, and also my Mum's Android tablet over the internet. Since yesterday I've been unable to connect to any of them. I get a "Starting Host App" message, then it stops trying to connect. If I then try to connect again I get a "Connection could not be established" error.

Two of the tablets are Samsung Galaxy Tab A's. The other is a Lenovo Tab 4.

Any idea why this has suddenly stopped working? I'm using the free Teamviewer/personal use service.