You can read about how the issue begun here.

After the fiasco that was the latest Windows 10 update, Microsoft have decided to put the update on hold until it figures out what exacly went wrong. Upon visiting Windows’ official website you will see that the latest Windows 10 update available is the October one. Message on the site’s support page states that ”We have paused the rollout of the Windows 10 October 2018 Update (version 1809) for all users as we investigate isolated reports of users missing some files after updating”. We shall see how Windows deals with the issue.