Outlook VSTO Add-In loads, but ribbon doesn't

Question

I'm making an Outlook VSTO Add-In with a ribbon and the ribbon stopped loading. I'm using the Ribbon (Visual Designer). It was loading fine, I made some code changes, fired up a new session, and it wouldn't load. There is no "Add-Ins" item in the ribbon.

I think the problem is in my Outlook, not in my project.

I created a new project to make sure there wasn't something wrong with my larger project, using the most basic code with no code in the addin class and only a single group in the ribbon. It still won't load.

• ThisAddIn_Startup is firing, so I know the addin is loading in Outlook
• I've tried both Ribbon Designer and XML
• RibbonType is set to Microsoft.Outlook.Explorer
• I've deleted all .vsto files and removed references in the registry
• I've rebooted

Answer 1

First of all, I'd suggest making sure you don't have any ribbon UI errors at runtime. Here is what MS states:

By default, if a VSTO Add-in attempts to manipulate the Microsoft Office user interface (UI) and fails, no error message is displayed. However, you can configure Microsoft Office applications to display messages for errors that relate to the UI. You can use these messages to help determine why a custom ribbon does not appear, or why a ribbon appears but no controls appear.

See How to: Show Add-in user interface errors for more information.

Make sure that you did all the steps described in the following articles (one of them):

• Walkthrough: Create a custom tab by using the Ribbon Designer
• Walkthrough: Create a custom tab by using Ribbon XML

If you use the ribbon XML approach you can set up a breakpoint in the ribbon's getCustomUI callback to make sure the callback is invoked and what ribbon XML is returned.