You didn't mention whether you did the Check Switch on the old receiver. I know that the customer probably wouldn't want you wasting your time trying to get the old receiver working, since they are upgrading anyway. However, I was thinking that since you swapped the LNB, a Check Switch may still be necessary to get the old receiver to recognize the new LNB for both tuners. If it still doesn't work after the Check Switch, then it could just be a case of the separator being incompatible with the DPH LNB. That still would not rule out the possibility of two cables directly from the DPH LNB to the dual-tuner receiver (without using a separator) working properly. It may be a fun experiment for someone who has the equipment and the time to try it.