The documentation on this page has been and is incorrect and mis-leading. (Upgrade apps—Web AppBuilder for ArcGIS (Developer Edition) | ArcGIS for Developers ) When the downloaded file is extracted, the new web appbuilder is placed inside a folder called WebAppBuilderForArcGIS. Therefore to upgrade previous version Apps, the typical path will include this folder. ex:
Hi Robert, thanks for your comment.
Was a little frustrated at time of my post and was fixated on a running service looking for node-js!
The service running was actually "ArcgisWebAppBuilder", when I stopped the service I removed the locks on the active folder. This allowed me to rename and replace with new v2.18 WABD.
All good now.