Buttons for compiling Themes and Wigetsets

Installed Eclipse Neon on new machine. Copied the project, but the buttons for compiling themes and wigetset are not working. Plugin for Vaadin is installed.

No plugin found for prefix ‘vaadin’ in the current project and in the plugin groups [org.apache.maven.plugins, org.codehaus.mojo]
available from the repositories [local (C:\Users\username.m2\repository), vaadin-addons (http://maven.vaadin.com/vaadin-addons), central (https://repo.maven.apache.org/maven2)]
→ [Help 1]

​Somebody an idea? Not sure what to do…

The compilation always just worked… No one wants to help?