An update have been posted.
WorldWind team would like to inform you that starting April 5, 2019, NASA WorldWind project will be suspended. All the WorldWind servers providing elevation and imagery will be unavailable. While you can still download the SDKs from GitHub, there will be no technical support. If you have questions and/or concerns, please feel free to email at:
That is a quote from https://worldwind.arc.nasa.gov/news/2019-03-08-suspension-notice/
This affects Mapton and it’s users since WorldWind is one of the map engines used in Mapton.