Audio not importing into Storyline from old Articulate ppta file

I know there are rather old  discussions on this subject, but I'm not having any luck despite following all the troubleshooting suggestions in them. When I import an old Articulate presentation into the latest version of Storyline, it works well enough, but the audio doesn't make it into the imported slides! It's a significant problem for us, since we have a number of courses to revise from 2012! I really hope there's something simple I'm missing. The files are not on a network drive, fwiw.

Thanks!