PyCharm plugin not detecting Python

I have a plugin that has:

<depends optional="true" config-file="plugin-python.xml">com.intellij.modules.python</depends>

plugin-python.xml is loaded:
Windows IDEA Ultimate + Python plugin
Windows PyCharm Professional when run through IDEA Ultimate debugger (shows Python plugin as unchecked and in red)

plugin-python.xml is not loaded
Windows PyCharm Professional (does not show Python plugin)
Linux PyCharm Professional (does not show Python plugin)

I know the non-optional part of the plugin loads because I log to the event log.

Why isn't doesn't the plugin-python.xml file load with the standalone PyCharms?

-Charlie