I've only been having this exact problem recently; whenever I try to play audio from my laptop (HP Pavilion 15-n271ea I think​, x64) with my headphones (3.5mm jack, Sony) the audio plays through my speakers and not my headphones. This would happen before (with audio playing through the headphones as well as the speakers) but would always be resolved if I restarted my laptop; no such luck now. All of my drivers are up to date (apparently), and I've gone into the sound settings, everything's at default, etc etc. No option for headphones, just "Speaker/HP".

Been into the DTS Audio Control panel and pressed a few buttons, to no avail.

I can upload specs if that'd be of any use; I've been scrolling through various forums for a few hours now and trying what I can, but nothing's worked.
(I use Windows 10 Home v10.0.14393 Build 14393.)

Thank you in advance.