ServerShield by CloudFlare extension cannot be switched from Free version to Plus version: no Recheck License option available in Server Dashboard.
Installed version of CloudFlare is less than 1.8.6
Every Plesk 12 license includes free version of ServerShield by CloudFlare by default. Plus version is available as a paid add-on. If license contains paid add-on ServerShield Plus by CloudFlare, it is required to enable Plus version.
To enable ServerShield Plus it is required to manually recheck CloudFlare license to update free version of ServerShield to Plus version according to Plesk 12 ServerShield Installation Guide.
If Recheck License option is missing in Server Dashboard tab, upgrade ServerShield by CloudFlare to 1.8.6 version in Extension Catalog. If Upgrade option is not available, remove CloudFlare completely, then install it again in Extensions Catalog (only the latest version will be available for installation).