Dell R530 no POST with second E5-2697 v4

I have a R530 running with 2 x 2698 v3 and I want to upgrade to use 2 x 2697 v4. Each CPU was verified and works just fine when installed in CPU1. When both CPU are installed, the server does not POST, no video signal. 
I have  latest BIOS and latest iDrac. The power supply is a 1100W.
Any suggestions?
Thank you!