@windaws97 I tested this and could replicate it: pasted the same song (Was Ist Ist by Einstürzende Neubauten), in format mp3, 128 kbit/s, in every Custom Music channel I have in my game: Hiphop; Island Radio; Electronica; Easy Listening; Classical; Blues; Baroque; Alternative; Jazz; Kids Radio; Lullabies Radio; Pop; Romance; S-pop; Spooky; Winter Holiday; World; and Strange Tunes. The song played on all of them, except Strange Tunes. I took my sim to the bar "8 Bells" in Strangerville and the song played on the channels there; but not on the Strange Tunes. The song does show up in Game Options>Music, under Strange Tunes channel; and I tried to toggle it on/off, that did nothing; and also to turn off all the other songs. That just made the station quiet, although the music tone animation still played, and my sim could listen to it and get a good moodlet from it (Music Lover).
I could not find an existing bug report for it, but the advise in this old bug report for custom music not working is to make a new thread if only one channel isn't working, see post #34:
https://answers.ea.com/t5/Bug-Reports/FIXED-Sims-4-won-t-play-custom-music/td-p/4453314
Here is how to make a bug report:
https://answers.ea.com/t5/Bug-Reports/INFORMATION-How-does-this-forum-work/m-p/3445427#
Please do, I want to Me Too on it 🙂