Skype not in headset but OK on speakers iPad iOS6

On our iPad that still has iOS6, Skype works with the iPad speakers and microphone but when we plug in the headset the sound is EXTREMELY quiet almost totally dead and the mike doesn't seem to be noticed by the iPad - the iPad mike is still the one picking up sound - so cannot use the headset.

The iPad sound is NOT on mute - checked. Normal earbuds for music work OK.

The iPad sound is NOT pushed all the way right or left - it's in the center. (Also tried the Mono sound switch - did not help.)

The iPad Notifications and Alerts for Skype are ON.

This is Skype version 4.17.0.123 (4.17.123).

We noticed that the plug for the headset has four segments but the plug for our music earbuds has three segments. (To describe it a different way, the plug for the headset has a tip and three rings above the tip but the plug for our music earbuds has a tip and two rings above the tip.)

The headset is a Native Union 'Pop' Phone. It works when plugged into other devices.

Have checked MANY forums but no help (unless I missed something).

Ideas? Thoughts? Thanks!