One or more fields in the document have been set up to use a Plugin, but Plugins have not been enabled.
If you have Plugins installed on your system already, simply clicking the plugins button on the Tool-bar enables them. (If a field uses a plugin and plugins are not enabled by default then you will be prompted to enable them.)
If Plugins have not been installed on your system yet, you will need to enter a permission code. This is supplied when you buy Plugins: please contact email@example.com.