If you used the option to keep SSL-protected and all other content in separate directories, and had APS-packaged applications installed in the httpsdocs directory of a website, then after upgrade, Plesk will switch on the compatibility mode for that site. This will make the apps previously installed into httpsdocs directory accessible to the Internet users, but the apps will not be manageable through Plesk, and you will not be able to install new apps to the httpsdocs directory.