GNOME and Java tray applications

Folks;

internally we build an application that comes with a Java GUI and 
includes a system tray icon for interacting with the application. While 
this works pretty well on all the other machines in our environment 
(MacOS, Windows), it doesn't at all do so on my GNOME desktop. Outcome:

- In the GNOME (3.18) notification area, I just see a black square where 
the icon should be.

- The icon itself can be found as sort of a mini-size application window 
top-left of the screen, just below the "Activities" menu.

- Context menus on the icon don't work at all.

I am unsure what's the problem here; I just recalled that earlier 
versions of Java system tray integrations _used_ to work with earlier 
versions of GNOME out of the box. Any recommendations that can be made 
on how to get this to work?

TIA and all the best,
Kristian