I have an HTC one. It refuses to recognise any headphones. It's brand new, I just had it replaced because of a camera problem. Within a few weeks of gettting this replacement, this problem started. It would not recognise any of my headphones. I even tried following a YouTube video's advice of backing up, doing a factory reset and restoring. This made no difference. Although I was convinced this was a software problem (because the phone is so new0 I am now convinced that it is A HARDWARE PROBLEM because the advice given here to ram the jack in as hard as it will go SEEMS TO WORK ! HOORAY !!
My previous identical HTC One that I got around 18 months ago started exhibiting this same problem after I'd had it around 6 months, but then it seemed to be sensitive to only certain sets of headphones. I now realise that it is probably the sublte difference in length of the jack that might be the issue here.
Anyway, clearly this is a hardware design flaw with the HTC One. and a very annoying one. Not having music or use of headphones for calls for me is like losing 50% of the functionality of the phone.
What are HTC going to do about this ?