Getting sound files into Camtasia...

 I downloaded some files from our Panopto recording area using advice from here:

https://support.panopto.com/s/article/How-to-Download-Video-or-Audio-Streams-as-MP4s

This allows download of audio and video separately - I downloaded as MP4. 

Camtasia couldn't generate any sound from the MP4 files. 

This site told me to use Audacity to do this: https://support.techsmith.com/hc/en-us/community/posts/360071641332-Importing-MP3-audio-file-into-Camtasia-8-1

Audacity required the use of a library: https://manual.audacityteam.org/man/installing_ffmpeg_for_mac.html

This allowed export of a Wav file. 

Camtasia can use the Wav file. 

Took a while but all in all quite good.