Download Nvidiainspector here.
Open up the driver profile settings (tool button next to driver version).
Go down to "SLI compatibility bits (DX1x)" and select the following:
0x080116F5 (Act Of Aggression, Battlefield 3, Battlefield 1, Battlefield 4, Battlefield: Hardline, Dragon Age: Inquisition, Need for Speed, Medal of Honor: Warfighter, Plants vs Zombies Garden Warfare 2, Star Wars: Battlefront (2015), Plants vs Zombies Garden Warfare)
That should allow SLI to work properly.
Need a screenshot of the result and GPUz
Need GPUz screenshot as well to be added to the board.