After upgrade to Sisyphus an icon for NetworkManager is lost. Not shown either in KD4 or in KDE5.
I don't sure that this is a problem of nm-applet. More likely it is something on the side of the current GTK3 and KDE itself.
Is there any chance you can try some other GTK3 panel applet in the KDE?
The problem appears both in KDE4 and KDE3.
I am not using GNOME, please tell me an example of GTK3 panel applet to test.
Bluetooth and blueman are shown OK.
Works in kde5-5.0.0-alt27