If you’re an iTunes Match user, you certainly recall that iTunes, before the current version, had an Update iTunes Match menu item, in the Store menu. With iTunes now, iTunes Match is no longer the term used (which is confusing), and your iTunes Match library is part of iCloud Music Library. But there is no Update command in the Account menu (the one that replaces the Store menu).
The iCloud Music Library should update automatically, but as iTunes Match users know, that wasn’t always the case before, and probably won’t be the case in the future. If you ever want to update your iCloud Music Library manually, choose File > Library > Update iCloud Music Library.