Personal Music doesn't play on Chromecast

[randiftw]

I have files that I added from iTunes on my Spotify Desktop. I added them to a playlist and made them available offline. I can listen to them on my iPhone no problem. If I try to chromecast the playlist from my iPhone, any of the personal songs do not play. They either skip or if I try to cast that song directly, my chromecasts are not options to cast to.

Help is appreciated! Thanks!