Listen button not working

I always use the listen button to solo an FX track, but suddenly it has stopped working properly.
I know what you’re thinking…my control room isn’t set up properly. I’ve attached a screen shot of my CR settings, which should be correct. Any yet, when I press the listen button on any type of track, nothing happens.

Listen

It works as expected, here. When saying that ‘nothing happens’, is it a visual issue or an audible one (no attenuation of the other tracks) ?

For now, the only things that come to mind are both the PFL/AFL toggle in the Control Room Main section and also the faders position of the involved tracks relatively to the Pre/Post Fader send setting of the sending tracks. A mixture that can become confusing, in this case…

Problem solved. The listen button on the master bus was on!