The major change for Mac OS Sierra is that it removed Run App From Anywhere in the settings. myTaxExpress and T2Express software are not listed in App Store. You need to do the following to run the software.
1. After you download the app and move it to your Applications folder, right-click on it and select Open.
2. After you select Open, you will see a warning that's similar to the one below. Click OK to open the app.