Always give zero output from grove i2c

Hi, I’m trying to use 8-Channel 12-Bit ADC for Raspberry Pi (STM32F030) connected with raspberry to detect voltage. I’m using the example code from grove lib adc_8chan_12bit.py. All the channels keep giving zero results.

i2cdetect is working:
pi@raspberrypi:~ $ i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: – -- – -- – 08 – -- – -- – -- –
10: – -- – -- – -- – -- – -- – -- – -- – --
20: – -- – -- – -- – -- – -- – -- – -- – --
30: – -- – -- – -- – -- – -- – -- – -- – --
40: – -- – -- – -- – -- – -- – -- – -- – --
50: – -- – -- – -- – -- – -- – -- – -- – --
60: – -- – -- – -- – -- – -- – -- – -- – --

i2cget is:
pi@raspberrypi:~ $ i2cget -y 1 0x08 1
0x00
pi@raspberrypi:~ $ i2cget -y 1 0x08 0
0x00

I have double-checked all connections even tried changing another board. But the problem always happens. And I also used a multimeter to detect the voltage, the multimeter shows correct result but the i2c still get 0:
image

What should I do now? Thank you so much for any hints.