no sound with video recording

[rikona]

Running Ubuntu 16.04 updated. Trying to record some screen video plus
audio that is on a FF browser window. The video plays just fine, and the
audio is okay to headphones - the way I usually watch videos on this
box. The installed FF extensions to record video don't work on this
screen. Tried a couple of screen video recorders, Kazam and Vokoscreen.
Kazam didn't work for either video or audio. Vokoscreen worked for
video but does not record any audio. Vokoscreen offers three possible
options using pulse, and two possible options using alsa. The audio box
is checked, so it should record. None of these possibilities will
produce recorded audio.

Ubuntu sound settings are currently set to line out, which goes to the
headphones. The other possibility is digital output - both of these use
built-in audio, with analog stereo output set for the line out.

What do I need to do to enable Vokoscreen to record the audio as well
as the video? And, how do I get any additional information that might
help to analyze the problem and fix it?

Thanks...