ADC121C021 Reading Issue

I’m trying to read values using the recommended library here:

It seems to work - but no matter the input voltage I read a value of 4095 (the maximum) out?

As a signal I am using AD5667 board and able to read the correct output with a multimeter. Does there need to be a load (resistor) between the output of the AD5667 and input of the ADC121C021 to read the proper value?