Emulated Hue, Alexa and Lutron - no dimming

I have full dimmer control over my 6x channel Lutron system directly through homeassistant which works perfectly

However, Alexa (through Emulated Hue) will only turn on and off the Lutron channels (works perfectly) - but if I ask it to ‘set brightness to 50%’ Alexa will come back and say ‘please check the device is connected’.

Any ideas?