Similar to OXI OUT, the dot will be only visible when the Ioniser is running and when there is no dot, it is not working.
For example, at 20% the dot will be ON for 2 mins and OFF for 8 mins as this works in 10 minute cycles.
The default setting for the Ioniser is 20% and will only operate in TIMER 1 based on the volume of your pool entered.
If your pool is in an environment where it is under heavy demand, such as a lot of garden surrounding or trees overhead, you may need to increase the Ioniser default setting but always do this incrementally while monitoring copper levels ensuring they maintain in the pool at levels between 0.2ppm - 0.5ppm.