As long as your lights are on, you’re still being supplied with energy and the meter is recording your usage. If you can’t see the electricity on your IHD, it may mean the meter is not connected to the IHD.
Try moving your IHD closer to your electricity meter, turn the IHD off, wait a minute and turn it on again. If after 48 hours your IHD is still not displaying data for both fuel types, get in touch.