FFmpeg and AMR files

I have FFmpeg properly loded in the Library; all three editions show up.

I opened an AMR file, took some time to open, but then played the file with no problem. Onto file 2, and every file thereafter: upon opening or importing, the track window instantly opens but there is no audio. PLAY=silence. Just a straight line for each file. What Happened?

Does that file still work in Audacity? Can you still import it into Audacity?