iPhone 5s won't connect to Apple Carplay

I have a new Hyundai that supports Carplay. I successfully connected my iPhone 6s to Carplay without issue. However, I have been unable to connect my girlfriend's iPhone 5s. The car identifies the phone and I can use Siri, but not Carplay. On the phone, under General -> Carplay, my car will not show up under "available cars", including when the phone is directly plugged into the car via usb.

Any ideas?! Thanks!