You have recently updated to Kerio Connect version 9.3.1 patch 2, and you find that the Antivirus engine is not working properly. You might be getting an AV timeout.
Please perform a complete redownload of the Antivirus database by following the process in the article "Resolving 'Antivirus check cannot be performed' error".
This should resolve your issue.
Should Antivirus still fail after that, it might be a connectivity issue. If so, please try the steps in the following articles (in this order):
- Run the installer. Click Next on the welcome screen.
- Select the Repair option and click Next.
- Select the Keep current configuration option and click Next.
- Click Install.
- Wait a couple of minutes to complete the repair process, then click Finish.