Update, June 14, 13.15pm: We could solve the issue in the meantime and planning works as usual again. 

As of June 14, 11.30am, we've started receiving many reports of an error message that appears when editing or planning a Tour that says: "An error occurred. Your Tour could not be planned successfully. Try and commit the action again, and if the error persists, try repositioning the latest waypoints."

Our developers are looking into it now and we hope to fix it as soon as possible. We will update this article once it has been solved.