The F4 SPI_SDO pin is linked to all SPI chips of the ADAC250 and routing of the SDO signal is switched by the chip select pins. Make sure all chip select are high except the ADC chip select (E3 pin) and try to read a known value. You can also try to write then read back a value.
I am able to read/write values in the DAC5682Z chip, but not in the ADS62P49 chip. Why is that?