XPA-2 - issue - speaker - advice needed !

Morning - I have a relatively simple setup  -  Yamaha R-S700 two-channel receiver; Emotiva XPA-2; Polk Audio RTI-A9 tower speakers; and Bose bookshelf speakers.

Before I installed the Emotiva, I was running four speakers through the Yamaha receiver.  When I installed the Emotiva, I removed two "jumper pins" from the coupler port and installed the Emotiva jacks into the "Pre Out" port.  Now, when I power the system up, I only get sound from the Polk speakers hooked up to the Emotiva.  If I remove the Emotiva jacks from the Yamaha receiver and replace the jumper pins, I get sound from all four speakers again.  What am I doing wrong?  Thank you much.
Your Yamaha has a pre-out/main-in feature, which is to allow something like a MiniDSP to be added. Since you connected the Emotiva to the pre-out, the Yamaha’s internal amp is no longer getting a signal. To fix this, simply buy RCA splitters (or mono male RCA to dual male RCA cables), so from the pre-out jack, one of the split signals goes to the Emotiva and the other goes back into the main-in port on the Yamaha.
Thank you for the response and advice  -  -  much appreciated - will do so.   Fran

"mono male RCA to dual male RCA cables"

Actually dual male to single female will work much easier. The 2 males into the Yamaha and the single female for the cable going to the Emotiva. Like this,