In order to update the database of Malwarebytes Anti-Malware, you should check if the "Download Now" section from the Dashboard tab of the GUI is active and click it. If it's not active you should check the following:
- You need to install Malwarebytes Anti-Malware from a Windows Admin-level account.
- Verify that your antivirus software and firewall both give Malwarebytes Anti-Malware full permissions because it is possible that any of these two might be treating the new build as a new program and may be blocking it.
- Verify that there are no detected threats needing your attention by clicking the "Scan" button at the top of the dashboard.
If none of this helps you, try uninstalling your current version of Malwarebytes Anti-Malware and reinstall the latest build.