I am using the indicator-systemtray-unity for quite some time; and initially, it worked really good for me: I clicked the indicator, and it would display a little array below the indicator; containing all the systemtray icons.
At some point, something strange happened ... I don't know what caused it, but now the system try icons were always showing up. In the middle of the Unity "top bar" there was now a section that constantly showed the icons. I have found no way to disable that, but I didn't see that as a big problem (actually: it was quite nice: the icons were always visible).
But: I am using a laptop. When the laptop is the in the docking station, I am only using two external monitors; I normally keep the lid of my laptop closed.
Now my problem: since lately ... the system tray icons are no longer shown on my external monitors. When I open up the lid of my laptop, the icons are still there, in the middle of the "top bar"; but they don't show up on my external monitors.
In order to fix this problem: a) I ran sudo apt-get --purge remove indicator-systemtray-unity ... and re-installed b) I tried clicking on the little button, but no matter what; any left/right click just pops up a "Settings" dropdown, which pops up another dropdown ("Backgrounds"); and making changes there doesn't seem to have any effect.
So, long story short, is there a way to reliable "reset" the indicator, so that it only shows the icons when I click the indicator?
Btw, I am running 16.04; but I encountered similar issues before, when running the indicator on 14.04.