Same as me.
Check the advice from
dedeca.
In short, downgrade to v5.14.2, connect to Wi-Fi for a few seconds until the "Display Cover" option comes back, then go offline and reinstall 5.14.3.2.
- I always reinstall JB hotfix after installing firmware.
- Backup /var/local/KWISClient.db, when it working.
- Decca suggestion: avoid rebooting the device when online.