WordPress users – do an update now!
The WordPress 4.9.3 update introduced an updating bug: after auto-updating to 4.9.3, WordPress will no longer update automatically.
What to do?
WordPress has published an explanation of the bug and detailed instructions for “handraulic” updating; the TL;DR version is:
Simply visit your WordPress Dashboard → Updates and click “Update Now.”
Source: https://nakedsecurity.sophos.com