I spoke with the operator using this DSS and here is what she told me.
If a call comes in and she presses the button, absolutely nothing happens. No tone, no disconnect, no nothing. She said it is as though she does nothing.
However, if she is off the phone and just presses the button as though she is just calling the extension herself, it will ring and connect.
Strange, no?
We are also going to try assigning the extension to a known working button and see what happens.