dark: not working

[shiftlabs1]

Can anyone help me understand this statement in the readme

 // use the .ns-dark class to control dark mode (applied by NativeScript) - since 'media' (default) is not supported.
      darkMode: ['class', '.ns-dark'],

As when i use

bg-teal-500 dark:bg-cyan-700

for example , the styling does not get applied when using dark mode on the phone, only the default bg-teal-500 is ever applied . I even added it as a plugin in the config

  plugins: [
        plugin(function ({ addVariant }) {
          addVariant('android', '.ns-android &');
          addVariant('ios', '.ns-ios &');
          addVariant('dark','.ns-dark &')
        }),
      ],

still no Joy. What am i doing wrong

Thanks