MinimWatch no X11-Window

[simoncn]

You are running Java 8 (1.8.0_201). To get the X11 window working with GNOME Shell, you need to be running Java 9 or later.

I don't know whether Debian Jessie has an apt-get package for the correct version of Java. If this isn't available, an alternative is to disable MinimServer desktop integration and run MinimServer from a Terminal window using startc or startd.