1. Extracted the 2-file contents of the Plugins folder (ConfigurationManagerLibrary.dll and mb_Spectrogram-Display.dll) into the MB Plugins directory, and started MusicBee.
2. Without entering prefs/plugins, immediately receive message to place 3 files--ConfigurationManagerLibrary.dll, ffmpeg.exe and config.xml--into the MusicBee directory. Note that the readme says to ALSO put ConfigurationMenu.exe there, so did that as well. Then, went to prefs/plugins and enabled plugin/save. Restarted MusicBee.
3. Went to configure layout and dragged spectrogram entry to bottom of Main panel, where it appears just above the bottom panel player controls.
4. Began to play a song, no spectrogram is displayed. Opened the settings panel by clicking in upper left corner, opens fine, saved default settings and option to remove png's on restart. Still no display; however, clicking inside the empty spectrogram window does seek through the song.
5. Restarted MB, still no display. I do get a "Spectrogram images deleted" message upon restart, confirming the setting I made in its options. Just don't get any visible waveform. Tried disabling/re-enabling plugin, also removing my Classic Spectrum graphic vis from the right sidebar, still no-go.