I have connected a SI7021 in parallel on the I2C bus to rule out connectivity issues.
I can detect the SI7021 on the same I2C bus but not the NCD PR33-15?
Try putting two pull-up resistors at 3.3V on the raspberry pico side, disconnect the SI7021 sensor and check if you can read the address of the NCD PR33-15. also check that your cables are in good condition.
I hooked it to an arduino, and connected it directly to the PR33-15. I used the onboard pull-up resistors. I used the code provided in the link.
I get nothing from the ADC.
It’s very difficult for us to provide technical support on the i2c products. There are so many variables that can interfere with functionality. The only way we can provide support for connecting to a Pi is if you use our Pi I2C interface adapters:
These adapters handle voltage adaption on the SDA and SCL lines.