First of all, you need to make sure the add-in is loaded by the host application. Try to set a breakpoint and start debugging from VS. If any breakpoint is hit then you need to start working on the ribbon errors. If not, you need to check why the add-in is not loaded by the host application. There are multiple reasons why the add-in may not be loaded, see How to troubleshoot a VSTO addin that does not load? for more information.
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.
To show VSTO Add-in user interface errors you need:
- Start the application.
- Click the
File
tab.
- Click
Options
.
- In the categories pane, click
Advanced
.
- In the details pane, select
Show VSTO Add-in user interface errors
, and then click OK
.
See How to: Show Add-in user interface errors for more information.