I have 10SRL-F's with E5-2680v4's on 3.3. they used to have E5-2678v3. During my CPU swapout one of the boards refused to post with 2680v4 but worked with 2678v3. I swapped the 2680v4 into another board and it worked fine. I used a magnifying glass and found some lint on a couple of the pins and one was slightly bent.
Indirect canned air removed the lint.
I straightened the pin using a lighted magnifying lens, and the barrel on an empty pentel .5mm mechanical pencil.
my suggestions:
pull the cpu.
check the pads on the cpu and if necessary clean with appropriate cleaning fluid and let dry before re-installing.
check the motherboard cpu socket for lint, bent, broken or dirty pins.
carefully clean any dirty pins
gently, sparingly, indirectly, use canned air to clean out the cpu socket to be sure.