Importing audio causes playback to stop working

Hello all,

Working with Adobe Premiere Pro 2023, on Win 10.  I initially had problems getting playback to work, had to adjust Audio Hardware Device Class to ASIO to get playback to work.

I have a project that has one audio clip from an MP4 video animation, and that plays nicely.

However, when I attempt to add another single channel mp3 wav, playback stops working.

Recommendations on what to do to resolve here?

Thanks!