x99 board tutorial but maybe it will send you in the correct direction:
 
https://forums.evga.com/X...-BY-STEP-m2476830.aspx

Did you install the Samsung specific software and drivers? Although the Windows driver will usually work, I have heard of people having trouble with the windows NVMe drivers. The Samsung drivers will give you better performance as well. Does the drive still appear in the BIOS?

I have 2x 950 pros in my system (I have the Classy-K, but the same principles should apply). When I get home tonight, I will try to check and see if there any specific settings that might be causing you trouble. The only other thing I can suggest right now is double check the seating of the drive in the socket if you haven't already.

I suppose I could just have a bad drive. But it doesn't make sense that I was able to use it briefly.

The drive and M.2 slot are both PCIE. I do not have any sata cables in slots 5-6.
I have the 960 showing in bios now, but I still can't boot from it.
I messed with it this morning and windows in now saying I have an NVM express controller driver error. And the trouble shooter can't seem to fix it. I don't know if that's a problem with windows, my board, or the drive it's self.

Also it's ok gbaker3, I'm still figuring out a lot.

You might just want to read NOTE below: I have used this for many years.
 
To check and see if you have old drivers you just uninstall; you must set a flag for device manager from the cmd box.  Right click on the Command Prompt and click on Run as administrator.  
 
Now type in this  FLAG/CMD:  “set devmgr_show_nonpresent_devices=1” (no quotes) 
 
Next type ”devmgmt.msc “  (as administrator)
 
Once you are in Device Manager, go to the "View" menu, select  “Show Hidden Devices”.  This will show all the device drivers including things that aren’t currently installed in your computer.
You can right-click on the (grayed out) driver(s) and then choose Uninstall from the menu to remove the old/unused drivers for that old hardware.
 
This procedure can resolve a lot of weird issues, and even increase performance on some machines where you’ve upgraded drivers.
 
NOTE: the grayed out drivers may OR may Not still be needed.  Before deleting make sure they are not for some devices (like USBs or some parts of media player).  

When I got my 960 I tried just imagining the drive but ran into some issues with windows, only after a fresh install with only the 960 connected did it work perfectly.