3:45pm CEST: We're investigating the issue.
3:55pm CEST: Not only starting, existing sandboxes do not seem to respond.
4:10pm CEST: We're shutting down existing sandbox instances and spinning up new ones. This will take a couple of minutes before the sandboxes will be available again. All existing sandboxes will be unfortunately deleted.
4:20pm CEST: Sandboxes are starting again. All previous sandboxes are deleted. We're sorry for this inconvenience.