Hi John,
Thank you for contacting Syncfusion Support.
We have created a simple VB sample for Ribbon based on your code in code behind and we can display the MessageBox when it has been loaded. We have prepared a simple VB sample to code with RibbonWindow for your reference and it can be downloaded from the below location.
Also, we suspect that you are inheriting the RibbonWindow from your application instead of inheriting your application from RibbonWindow in code behind based on your code. Can you please check with the above sample and let us know if we have misunderstood your query?
Regards,
Keerthana J