Amazon Echo Link and Multi Room play using personal playlist in Apple Music

I have my own Apple Music playlist I’m trying to play in the Amazon Alexa multi-room using the Echo Link and a 3.5 mm cable. However, it’s not working. I’ve tried all the input jacks. The music shows as playing on my phone but says the audio is playing through headphones. I have the echo link and two echos all connected in a multi room on the same WiFi. What else could i be doing wrong? Do i need a family plan or something to play my Apple Music playlist on multiple echo speakers? Anyone else have issues with this? Seems like most people find this to be a pretty straightforward process.