This can be enabled to display detailed error messages when loading VSTO add-ins, such as the Egress add-in.
1. Make sure Outlook is closed.
2. Select Computer Properties:
- Click Windows Start Menu
- Right-click on Computer and select 'Properties' (Highlighted below)
3. Locate System Properties dialog by selecting 'Advanced System Setting'
4. Select environment variables
5. Select 'New' and enter 'VSTO_SUPPRESSDISPLAYALERTS' with a value of zero (0).
6. Click 'OK' and restart Microsoft Outlook
7. Go to Options\AddIns in Outlook and try and enable the Egress Add-in. You should now get the full error of why the addin is not loading.