Hi Dave,
The widget name in manifest.json is not the same with the folder name
Github download: Experience-Builder-Radio-Layers-Widget-main
manifest.json: radio-layers
Thanks for posting. In the process of checking the widget out I was getting a message in the client folder prompt telling me the folder name didn't match the widget name. Your Github download has a different name than the widget name in the manifest.json. Once I changed the download folder name it was fine.
C:\arcgis-experience-builder-1.15\client\your-extensions\widgets\radion-layers