Lux Meter RS485 Problems

I’m using a DFROBOT RS485 Lux Meter and I can successfully connect to it via Modbus. I’m able to change parameters such as baud rate and device ID without any issues. However, the data in registers 0x02 and 0x03 is always 0, even though these registers are supposed to contain the lux value. Has anyone experienced this problem or knows what might be causing it?