Irig 2 not working on new- pre-2016 Macbook Pro retina

just got my Irig 2 to use on my new Macbook Pro (pre- new 2016 model)(but was built this year under old specs

Using Mainstage 3 for guitar effects

I've read elsewhere that macbook pros have issues with irig 2, so I watched a video where the guy bought an usb headphone adaptor to make thing work

I still can't get MS3 effects to work. MS3 does work just fine through my usb connected Presonus 44vsl unit. I purchased the Irig 2 to simplify use when only using on guitar.

Anyone out there use the usb adaptor to 3.5mm method and get it to work?