elfinder viewchange event not firing

[acdit]

Hi there.
I'm having trouble catching the viewchange event ...
I have this:

var elfinderInstance = $("#elfinder").elfinder(options).elfinder("instance");

elfinderInstance.bind('viewchange',
function(event)
{
... code ...
});

which does not work, and this:

elfinderInstance.bind('contextmenu',
function(event)
{
... code ...
});

which DOES work.
I've also tried it as a handler:

viewchange: function(event, elfinderInstance)
{
... code ...
},

but that doesn't work either.
Can anyone help me understand what's wrong? Thanks so much :)
Version 2.1.26 (2017-07-17)

Craig.