A small update has been made in the TOI Maya Toolbox for Mac users. It seems that the latest update/extension of Autodesk Maya 2016 is slightly different. TOI Maya Toolbox version 6.7.0 does not create the TOI shelf in Maya 2016 Extension 2.
We did not get any reports from Windows users having the same issue with the TOI Maya Toolbox as Mac users. Windows users can still download the Windows version (6.7.0) from TOI or Design Informatics.