If you had a previous version of the MAT App on your Mac, transmit all class data, then uninstall the old version of the MAT App. THEN Open the Safari browser on Mac - not any other browser. If you don't already have the Adobe AIR app on your Mac, go to www.adobe.com and download Adobe AIR to downloads. THEN, download the MAT App to downloads, then right click on MAT App and tell it to open with Adobe AIR. Then save the app to the dock so you can find it. (these install instructions are courtesy of Jill Gallier-Durand)