Why is my the output voltage from the internally connected PGA op amp to ADC outputting noise?

[harrypotter1]

For reference I have a nucelo G491RE board. Aim : I am trying to connect 4 sensors which have a low output signal to be amplified and then sampled by 2 ADCs (2 sensors are connected to one ADC). The problem is, is that I need a really high sampling rate like 1MHz but am struggling to read that even in binary in TeraTerm. I do not know what baud rate is required. I am using scan conversion mode for the ADCs. Although I can see the values appear alternating in the code, it does not appear correct on the serial terminal. Also the op amp is generating noise even it should read 0 volts. I havent even attmped to use the 2nd adc yet in the code becuase I cannot even configure the op amp correctly. can someone help?