Welcome to Nikonians! What mode do you have the remote SB-800 set in? Hint: The remote SB-800 Speedlight in the Phottix receiver will not work if it is set in remote mode. It must be set in non-TTL Auto mode or Manual mode. Also make sure that the Transmitter and Receiver are set to the same channel and group. Good Luck and Enjoy your Nikons!