Can you ensure you have latest BIOS and iDRAC FW installed on the server? What processor you had on the server before? Can you also try booting the server with single processor and memory in slot A1 and see whether server botting properly with new processor. You can try booting with both processor one at a time.
I researched and verified that dell T620 supports and is compatible with the E5-2695 v2  on the dell technical guide. I purchased and installed two new E5-2695 v2 and the T620 powers on but the screen is blank. Any help will be greatly appreciated.  References: [URL] E5-2695 v2 2.4Ghz 30M 8.0GT/s12 Cores 115W  
Poweredge T620 compatibility with intel xeon E5-2695 v2