I have an 18mz and the 7008 reciever. I have the three tail servos on an sbus cable. If I plug the cable into the SBUS2 port, the tail servos work normaly..If I plug into the SBUS port they don't work. My understanding is that they should work on either port. Is there a setting on the transmitter I'm over looking ?

What mode is your RX in? The SBus2 port is always active but if you don't set the mode to B or D then the 8/SB port will output CH8 or CH16.
Look at the second page in the attached manual.