That usually means your instruction line is missing one or more required values. This is the needed format:
#CommandName,ReturnType,ParameterTypes,Windows,Linux,Mac,Android,iOS,Windows64
And you need to fill in every field, even if it doesn't apply to the platform you are targeting. Additionally, you also need to include all possible parameter types for those within the function you are calling. So an example with several parameters for Windows might look like this:
MyCommandName,I,SFI,MyCommandWindows,0,0,0,0,MyCommandWindows64
Where 'SFI' is includes a string, float, and integer parameter as specified in the related command name function.