The individual memory modules on the DIMM have to match the addressing scheme of your motherboard or they wont work. All 8gb DIMM's aren't addressed the same way. I would have assumed talking to Dell would have been the best way to insure you're getting the correct memory type, but obviously that didn't work.
 
As mentioned above, the next best way is to go to crucial.com, use the search list to find your exact Dell model and buy from them. I've never had a problem with any memory I've bought from them, as long as the computer model is in the list.
 
Best Luck,
Steve

Received my 8Gb of memory tonight, it's installed and working fine! It's all good. Thank you to all. Case closed

Great news.

Good news.  As I noted its hit and miss with non-Dell branded memory (even the same brand as you bought). 
 
BTW, I'm originally from across the state from you.  Mechanicsburg.