Hi archerbob
First Alsa must be working, is Alsa working? can you test with speaker-test ?
If you've already installed PulseAudio and is running as per PulseAudio info file instructions then do not install Apulse, its either one or the other..
depending on the audio source firefox may need to switch between Flash or HTML5
If able to configure Alsa and alsa speaker-test passes yet Apulse still fails use Pulseaudio instead to configure sound source and output.
Also depending on the audio source you may find the extension "libavcodec.tcz" is needed
If still no sound load firefox_getLatest extension and use script at terminal in manual mode
firefox_getLatest.sh -m
to downgrade to last known Firefox version (Firefox ESR v52.0) with working Alsa. When prompted Enter
52.0esr
reboot without pulseaudio or apulse
I'll be honest here, On pc's where I'm constantly having to configure sound on every reboot I simply use "Firefox ESR v52.0" as above which reliably resolves the Alsa connectivity issue