I had this error when trying to package a plugin that required another plugin that was installed in my project.
Unfortunately, the packaging process only sees the plugins installed with the Engine (see Package Plugin when my PluginB is dependent on my PluginA), and won’t find your dependency.
The only solution I found was to install my dependencies in the Engine, but keep in mind that installing plugins on the Engine downloaded from the Epic Launcher will result in another error: “This type must derive from the ‘ModuleRules’ type defined by Unreal Build Tool.”
To be able to install additional plugins to the Engine, you will have to build it yourself from github.