Slideshow module - sync slide length to audio tracks

LR Classic 9.2.1 Release, Build 202004070813-7699d98a 2020

I, like many others, am having problems syncing audio to slide duration in the slideshow module.

I have recorded as .mp3 seven separate audio files (vocal narration), of different lengths. I have seven slides that I wish to change in sync with the audio tracks.

I think I have everything right - I have crossfade set at 1 sec. A couple of the audio tracks are longer than the 42.2 sec maximum on the slide length, which is what LR in Automatic mode set it to. I DO have the "Fit to music" button selected.

When I preview or play the slideshow, the audio tracks change, but all are played on the first slide - it never changes from the first slide to subsequent slides.

I have read through previous Qs and A's in this forum, and got no help. I tried the trick of replacing the "videotoolkit.dll" file as suggested once, only to have LR refuse to open; so I had to undo it.