"This add-in could not be started. Close this dialog to ignore the problem or click “Restart” to try again."

Solution
The solution depends on a combination of the version of your Windows operating system and your Outlook/Office which determines the browser used to render all of your Add-ins.

Note: This will be either Internet Explorer or Microsoft Edge. This is entirely different to the default browser which you have selected.

Determine if your browser is using Microsoft Edge or Internet Explorer to render your Add-ins

As the first part of the solution, determine if your browser is using Microsoft Edge or Internet Explorer to render your Add-ins. Refer to this Microsoft article Browsers used by Office Add-ins to determine this.

Then following the steps below as applicable for if this is determined as Microsoft Edge or Internet Explorer.

• If your browser is determined as Microsoft Edge
• If your browser is Internet Explorer

If your browser is determined as Microsoft Edge

Users on updated versions of Windows 10 and Microsoft 365 typically have Microsoft Edge used to render their Add-ins and it is possible that the Desktop App Web Viewer is corrupted. Take the steps below to reinstall it.

Please also contact the FYI Support Team at support@fyidocs.com to inform them.

1. Close all Office modules including Outlook.
2. Run the following command on your machine with elevated privileges.
   powershell Add-AppxPackage -register -disable c:\windows\SystemApps\Microsoft.Win32WebViewHost_cw5n1h2txyewy\AppxManifest.xml
3. Restart any Office module and load the FYI Add-in to check the issue is resolved.

If the issue is not resolved, following the steps below to repair the Microsoft Edge WebView2 application via the control panel:

1. On the affected user's computer, open Control Panel (in the Windows Search bar, type Control Panel).
2. Select Programs.
3. Select Programs and Features.
4. in the list of programs, locate Microsoft EdgeWebView2 Runtime.
5. Right-click over Microsoft EdgeWebView2 Runtime.
6. Select Change.
7. On the pop-up, select Repair.

Check if the Add-in is now working correctly. If the issue is not resolved, follow the steps below to Uninstall the Microsoft Edge WebView2 application via the control panel.

Note: Before uninstalling, note the following possible implications:

• Some web-based applications using Microsoft EdgeWebView2 may not work as expected.
• The component may be reinstalled automatically via Windows standard updates and may need to be removed again.
• Consult your IT consultant if you are experiencing any issues after uninstalling.

1. On the affected user's computer, open Control Panel (in the Windows Search bar, type Control Panel).
2. Select Programs.
3. Select Programs and Features.
4. in the list of programs, locate Microsoft EdgeWebView2 Runtime.
5. Right-click over Microsoft EdgeWebView2 Runtime.
6. Select Uninstall and follow the prompts.

If your browser is Internet Explorer

Microsoft renders Add-ins using Internet Explorer for users on older versions of Windows and Outlook.

Upgrade

As per the Microsoft article referenced above, users should upgrade to Windows 10 version 1903 or higher and Microsoft 365 version 16.011629 and higher.

Enable Protected Mode in the Internet Properties

If upgrading is not an option, then enable protected mode in Internet Explorer. Even though your default browser is not Internet Explorer note that Microsoft leverages Internet Explorer for users on specific combinations of Windows and Office versions.

1. Close Outlook and all your browsers.
2. Open Internet Explorer.
3. Click Tools.
4. Click Internet Options.
5. Click Security tab.
6. Select Internet Sites zone.
7. Select Enable Protected Mode (make sure box is checked).
8. Click OK.
9. Restart Internet Explorer and Outlook.
10. Try to reproduce the issue.
11. If the issue persists reboot your computer and try again.