How can I enable VSTO error/alerts to see why the add-in is being disabled?

This article applies to the following:
7.x Email Manager for Outlook
6.x Contributor Pro, Email Manager for Outlook

Issue: Email Manager for Outlook is not functioning properly and there is no dialog to explain what the issue may be.

Resolution: There is a Windows environment variable called VSTO_SUPPRESSDISPLAYALERTS that you can enable to display Outlook and VSTO error messages when VSTO add-ins are being loaded.

To enable the variable:

1. Close Outlook.
2. From the Start button, right-click Computer and select Properties from the contextual menu.
3. In the Control Panel Home section, click Advanced system settings. The System Properties dialog displays: 

   

4. On the Advanced tab, click Environment Variables. The Environment Variables dialog displays: 

   

5. In the System variables section, click New to display the New System Variable dialog: 

   

6. In the Variable name field, enter VSTO_SUPPRESSDISPLAYALERTS. In the Variable value field, enter “0”.
7. Click OK.
8. Launch Outlook. Ensure the Email Manager for Outlook add-in is enabled.