The developers didn't provide a way to download the updates manually, which means there could be 2 causes for the update problem:
- Internet connection is messed up. Start Internet Explorer then press ALT + T > Internet Options > Advanced > Reset. Additionally, check the Connection > LAN as well. Remove or fill the proxy field as instructed by your ISP.
- The update servers are down for maintenance. You should simply check back later, then you can update the antivirus.