RnCommTest starts in background

Dear all,
happens for some weeks now: after downloading and unpacking the RnCommTest the first few times it starts and works w/o any problems.

Suddenly it starts in the background: I see it active because the icon in the taskbar is acive and I can select it via ALT+TAB, but I never can get it in the foreground. Also selecting it via ALT+TAB and then hitting WIN+LEFT/UP/DOWN etc doesn’t work (it does with other win applications).
image

When using ALT+TAB or WIN+TAB it shows the RnCommTest-window but with only a black content. Looks like the start of the tool isn’t complete:

It is listed in the taskmanager (and uses RAM) but making a right-click there and selecting “to the foreground” also doesn’t work.

The behaviour is independend of using external screens or just the laptop screen. My win config:

Thank you very much for support.

Alex Bischoff