Hello guys
internal firmware can be found here.
In file code/UnitACMeasure/UnitACMeasure/Core/Src/stm32g0xxx_it.c in function Mycallback_handler() there is a check for the first byte received being 0x55 which means data is ok. So either the HLW8032 doesn't send 0x55 as the first byte after some time anymore or reading the 24 bytes from the HLW8032 somehow gets out of sync. In both cases this would turn off the LED. (Please note: this is just guesswork as I do not have the necessary hardware to test.)
As an alternative you could hardware modify the AC Measure Unit to bypass the internal MCU converting UART data into I2C; read the UART signal after the opto coupler and try this library.
Attention: please be careful when modifying the hardware. Only use the signal after the opto coupler.
Thanks
Felix