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Add-In Troubleshooting: “Add-In Could Not Be Started” and Other Issues


5 min read


If you successfully installed the Add-In and configured your corporate firewall to let RG Email Sidebar traffic through, yet on trying to open it in MS Outlook you get an error notification “ADD-IN ERROR. This add-in could not be started. Close this dialog to ignore the problem or click “Restart” to try again”, that might be caused an issue with RGES Sidebar rendering. This article describes the ways to resolve the issue. The solutions are only applicable for MS Outlook Desktop for Windows.



Solution 1: Refresh Microsoft Browser Configuration

The error may occur with various Add-Ins / plugins installed in MS Outlook Desktop for Windows. The below guidelines are official ones provided by Microsoft.

The first step is to determine the versions of Windows OS and MS Outlook that you are using. These versions define which native Microsoft browser is used to render MS Outlook Add-Ins; that might be MS Edge or MS Internet Explorer.

See this Microsoft article to find out which one is used in your system based on your Windows version and Office package version combination. Users running the latest Windows 10 and Microsoft 365 Office updates typically have their Add-Ins rendered by MS Edge.


If your system uses MS Edge

Sometimes the error is caused by MS Desktop App Web Viewer getting corrupt. Take the steps below to re-install this module.

1. Close all MS Office apps running in your system, including MS Outlook
2. Run the following cmdlet in Windows PowerShell or command line on your PC, with Admin permissions:

powershell Add-AppxPackage -register -disable {Windows folder on system disk path e.g. 'C:\Windows\'}\SystemApps\Microsoft.Win32WebViewHost_cw5n1h2txyewy\AppxManifest.xml

3. Run MS Outlook and try opening RGES Add-In to see if the issue was resolved




If none of Microsoft Add-Ins work or Sidebar controls become unclickable (WebView2 runtime)

The issue where important Sidebar elements become unclickable, e.g. the Save or Create button, has a technical cause on Microsoft Outlook side. Specifically, due to the ongoing Microsoft transition from old MS Edge to Chromium MS Edge some MS Outlook for Windows versions have an interface frames rendering issue with MS Edge. Microsoft is planning to roll out a complete solution in a future MS Windows update.

An official workaround provided by Microsoft:


The workaround works only for Windows 10 and Office 365 or Microsoft 365 package version 16.0.13530.20424 or newer. See this Microsoft article to learn how to check what version you have


1. Close MS Outlook
2. Close MS Edge browser windows, if any are opened
3. Download MS Edge Webview2 runtime from this location:

If this package does not work in your configuration, install an alternative version. Browse this Microsoft resource for versions compatible with different MS Edge builds and x86, x64, or arm64 architecture.


4. Open your Downloads folder and install Webview2 on your Windows system. The runtime’s security and stability are guaranteed by Microsoft, see this article for complete information on Webview2
5. Launch MS Outlook and check if RG Email Sidebar Add-In can be opened and key Sidebar controls are clickable




If that does not help



If your system uses Internet Explorer

In older versions of MS Windows and MS Outlook, Internet Explorer is used to render Outlook Add-Ins. There are several possible solutions for Internet Explorer:


Check your Internet Explorer

Make sure that you have the latest version of Internet Explorer installed, as described in this Microsoft article.

If needed, re-activate Internet Explorer in your Windows system:

1. Press the Windows key + R, type control and press Enter
2. Click Programs
3. Click Programs and Features
4. Select Turn Windows features on or off
5. Select the checkbox next to Internet Explorer 11
6. Reboot Windows to apply the changes, then check if the issue was resolved


Fix Internet Explorer Settings, if they got corrupt

1. Press the Windows key + R, type inetcpl.cpl and press Enter to open Internet Explorer’s Internet Options
2. Open the tab Advanced
3. Click Reset under Reset Internet Explorer Settings
4. Click Reset under Are you sure you want to reset all Internet Explorer settings?
5. As soon as the changes are applied, click Close and then OK
6. Reboot your Windows to apply changes, then check if the issue was resolved


Install System Updates

To get maximum performance and compatibility, all RGES users are recommended to upgrade to Windows 10 build 1903 or above and Microsoft 365 / Office package version 16.013530 or above.


Enable Protected Mode in Internet Explorer

In case upgrading is not an option, you can try enabling Protected mode in MS Internet Explorer. To do that:

1. Close MS Outlook and any web browsers you use
2. Press the Windows key + R, type inetcpl.cpl and press Enter to open Internet Explorer’s Internet Options
3. Open the Security tab
4. Click Internet Sites zone
5. Select the checkbox Enable Protected Mode
6. Click OK
7. Restart MS Internet Explorer and Outlook
8. See if you can open the Add-In in MS Outlook now
9. If the issue persists, reboot your PC and try again



Add Revenue Grid to Trusted Sites

If the issue persists after enabling Protected mode:

1. Press the Windows key + R, type inetcpl.cpl and press Enter to open Internet Explorer’s Internet Options
2. Open the Security tab
3. Select Trusted sites under available zones
4. Click the button Sites
5. Add * to the list
6. Restart MS Outlook and see if you can open the RGES Add-In now


Contact Revenue Grid Support

If none of the above listed solutions resolves the issue, contact our Support team for further assistance.


Also see the following articles:

“Browser version is not supported” troubleshooting

RG Email Sidebar mass deployment scenarios

How RG Email Sidebar works with EWS

Microsoft Consent framework

Microsoft App Consent Experience


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