Great Add-on, but for me it seems that eclips is not able to generate the w

Great Add-on, but for me it seems that eclips is not able to generate the widgetset. I am using Vaadin 8.1.0.rc1 and Eclips Oxygen 4.7.0.
Any help!

Did you include the vaadin-compatibility-client or vaadin-compatibility-client-compiled artifact in your pom.xml? See: https://vaadin.com/docs/-/part/framework/migration/migrating-to-vaadin8.html#widgetset-changes