I have the same problem: I have two whisperer and both report 0 Lux. One is on a terrace (directly to the south) and has 100% directly sunlight. The second one is in a greenhouse and has also free view to the sun, but Less light than the first one. Both report temperature and humidity but no lux.
2019-06-19 23:36:45
2019-07-05 06:05:55
2020-01-18 14:25:42