Copy your maya/2017/prefs/pluginPrefs.mel file to a folder which is not in your MAYA_PLUG_IN_PATH. If Maya now starts up without any problem look at the plugins listed in that pluginPrefs.mel file you copied and start flagging them for autoload a few at a time until you find the one which prevents Maya from loading.
If Maya still won't start up after moving your pluginPrefs.mel file delete your entire maya/2017/prefs folder.
If Maya *still* won't start up after that, start Maya from a command prompt (e.g. /Applications/Autodesk/maya2017/Maya.app/Contents/bin/maya). Scan the output which is displayed in your command window for any clues as to the problem. If you're still stuck, attach that output to your post here.
