Why won’t my IPhone 7 play audio through the headphone adapter?

When I plug in headphone adapters, my IPhone 7 doen’t recognize that they’re plugged in; instead, it just plays the music through the phone’s speakers. Oddly enough, the phone still charges normally, it just doesn’t respond to the headphone adaptors.

My phone 7 is running iOS 11.3 right now. I’ve updated it twice and the issue persists.