Certificate Manager plugin is listed twice on the plugins page because old one used one capital letter in the name (certificateManager.jar). I suppose this is also the reason Admin Console is not pulling this update and still have 1.0.0 as the latest version.
To be explicit, the response from the get available plugins query is a XML encoded map of plugin name -> plugin details. This map contains "Certificate Manager" twice.
The second entry (1.0.0) replaces the first (1.1.0). The PR attempts to fix this by ignoring the case of the JAR file.
To correct my first comment; it requires a case-sensitive FS for me to check.
Site fixed (not listed twice). Also Admin Console now found the update.