Spotify not playing with aux chord

[JenniferA03]

My Spotify works fine on my phone when I'm using headphones, but it will not work in my car when I plug in the aux chord.  I'd been using it like this with no problems until I was in a rental car for work for about a week.  I plugged in the phone in the rental using the aux chord once but decided to listen to XM radio instead for the week.  When I got into my personal vehicle and plugged in the aux chord, I couldn't hear the music even though the track was playing.

I did the usual--pressed AUX on my stero, made sure the chord was plugged into the car and the phone all the way, turned up the volume, and even bought a new aux chord.  Still no sound.

I noticed that it says "devices available" at the bottom now, and I never noticed that before.  My personal car doesn't have Bluetooth, but the rental did, and when I originally plugged the chord into my personal car recently, I saw that Bluetooth was on in my phone settings, but I don't know why. 

I feel like this is a settings problem since nothing in my personal car changed and the phone is working just fine.  Please help 🙂