The PlantUML Confluence Plugin depends on the Graphviz package. Please ensure that you have installed the package on your Confluence system. The Plugin requires JRE 1.6.x or higher (see also Supported+Platforms).
After the installation of the plugin you should check if the plugin was successfully initialized by adding the PlantUML macro with the body "version". Have a look at Note to Users of Confluence 3 and 4 if you are running an older Confluence version.
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