Hi Nicole,
I verified the operation on my ADS1248EVM before I responded previously. This means that there is either a setup issue, or an issue with the EVM itself.
Can you send me a picture of the EVM as it is connected using your setup? Also, make sure that the DAC switch on the MMB3 is in the OUT position (red colored switch on the left-center of the MMB3).
Thanks,
Bob B