Why are my wired headphones not been recognised?

My phone wont recognise my wired headphones through the usb c or a splitter.

The usb c port has been replaced so as the loudspeaker, I have tried multiple headphones, also tried the headphones on another device.

It charges perfectly, connects to my laptop fine, it just will not recognise my headphones.

Audio works fine via loudspeaker and bluetooth.