Lower the low threshold to 8 and raise the volume so you can hear the soft tone indicator.
Two things that new users often miss are:
It has to keep making the tone for the time delay. You can't hear that if the volume is too low,
and not every hole has a soft input configured. Look at the running configuration:
If the Soft pressure zone for a particular tube is not used, the audio tones are suppressed.
250 ms delay is fine. I would not go lower until you get the hang of it. If the delay is too low, you will not be able to get the pressure up to the hard sip/puff range quickly enough and only be able to issue soft sip/puffs, then you will likely need to erase the configuration files and start over.
Back up your configuration files to a folder on your computer.