SI Impact only two FX units working

jisenhower

Only two of the fx units work on my SI Impact. 1 and 2 work fine regardless of what FX I assign to them but 3 and 4 get nothing. I can solo out the send masters and hear the things I am sending to the FX busses but nothing comes back on the returns. I have checked the patches. I have read the manual. I have searched online. I have reinitialized the board. I am one step from calling Harman but am hoping someone here can solve my problem before sitting on hold.