Tip: If the add-in does not load when it should, you can debug it by setting the environment variables VSTOSUPPRESSDISPLAYALERTS to 0 or VSTOLOGALERTS to 1. VSTOSUPPRESSDISPLAYALERTS hides or displays dialog boxes when exceptions occur and VSTOLOGALERTS creates a log file in the same directory as the executing assembly, if an error occurs.

Problem: Add-in installs without error, but I don't see the Toolbar when I start Word.

References

Debugging Application-level Projects