The water level sensor works thanks to the minerals in the water.

Some waters have very low mineral content and therefore cannot detect the water level, which is why the light remains white.

Check the mineral content of your water:

You can find this information on the bottle labels: the mineral content is shown as ‘dry residue’ or TDS on the bottles and must be greater than 150 mg:

Most mineral waters work, except for those with very low mineral content (e.g. Montroucou and Volvic in France).

Tap water also generally works very well (except in certain volcanic areas where it is very low in mineral content).

To be sure it's a water problem, you can test by putting in a few grains of salt (after this test, throw the water away). The detector should turn green.