"No signal from RawAPI source" means technically that GetPCMRawData is not being triggered by MB. Maybe GetStreamInformation too, but CEN is a bit immune to that.
I couldn't reproduce it myself.
1. Find, download, whatever, a music file you are sure you have never played in MusicBee before or added to its library.
Not seeing it listed in your library is not good enough; it must not appear at all inside the MusicBeeLibrary.mbl file due to the bug being discussed
here .
2. Right-click the file in Windows File Explorer (not in any MB window like "Computer" etc.), and choose Open With-> MusicBee
3. MusicBee opens and starts playing the file; while the file is playing, on CEN select Source as "RawAPI Bridge"; the spectrum will cease with the message "No signal from RawAPI source".
4. While the song is still playing, change source to "MusicBee Native Fourier 2K"--the spectrum will return.
5. Run a "File Rescan" on the file (OR add it to the Library), and RawAPI Bridge will show normally again.
Be sure you don't accidently "scan" the file first by moving it within MusicBee, etc.
Note: this isn't being represnted as a "bug" per-se, just as a behavior eccentricity, demonstrating that files need to be scanned first manually or automatically by MusicBee before "GetPCMRawData" is triggered by MusicBee.