SendClick for buttons

Trying to use SendClick assigned to a keyboard, but can't get it working.

To test, I created a generic button button -

<control type="button" id="500">

  <description>button to toggle settings - for debug only</description>

  <visible>true</visible>

  <left>15</left>

  <top>15</top>

  <height>55</height>

  <width>55</width>

  <texturenofocus>defaulticonwarning.png</texturenofocus>

  <texturefocus>defaulticonwarning.png</texturefocus>

  <onclick>Skin.ToggleSetting(HideList)</onclick>

</control>

And then assigned a key -

<home>

   <keyboard>

        <F5>SendClick(500)</F5>

   </keyboard>

</home>

Pressing F5 generates this in the Debug log, so it seems to be working -
DEBUG: CInputManager::HandleKey: f5 (0xf094) pressed, action is SendClick(500)

But no action takes place.

From a search of the forum, all the prior questions seem to to be focused on using this to send a click to the control IDs that are part of the in the builtin windows, and not for a general application.   Is that the problem here?