Orbit in Maya 2016, 2017 stopped working

Probably an easy fix (hopefully).

I recently opened an old model in Maya 2016, when I click the mmb + shift keys I'm unable to orbit. I'm not sure if I accidentally assigned the orbit to a new set of command keys. I tried to repair Maya 2016 and restarting my computer to see if setting it back to the default settings would correct the issue, alas that didn't work. I've also just downloaded Maya 2017 (Student Version) and I'm experiencing the same issue. I've tried going into the Settings/Preferences --> Hot Key Editor to figure out how I can assign/check what Orbit/Pan is set to, however I'm unable to locate it. For the record pan is working in Maya 2017 by holding down alt+mmb, I can't figure out what my orbit command is.

I don't think it's a mouse or keyboard issue, as I can scroll using my mmb and my SHIFT keys are working to UppercasE letterS.

I'd greatly appreciate any tips/advice on how to resolve this as I can't work on my models without Orbit ..

Thanks!