The drop-down list allows migrating between antivirus solutions (ClamAV or Kaspersky). When the choice of an antivirus is made, the following message will appear:
"The antivirus database has to be fully downloaded before the antivirus can be changed. During this interval, the antivirus scan will fail.” Click on Switch engines to confirm your selection.
Once the database has been downloaded, the antivirus will be enabled.