Is there an adapter to convert from mini-jack to normal jack..? These can be delicate for some headsets.
Another detail... Are you sure it's a stereo headset, with only TRS (Tip, Ring, Sleeve...) contacts, and not a more modern 'phone-type, with an extra ring for mic or volume control..? These work for 'phones and some laptops, but need a different converter for normal, stereo, jack sockets such as your interface. Just a thought.