have you updated your BIOS and all that... depending on the board, it could have been made to top out at 1.2, then the company made a bios update to accept higher cpu's... so if you don't have the update your system will only recognize the highest that it was origanally made for.
Dell 4K S2817Q / Logitech Z-680 / Func MS3 Mouse / Corsair K70
NZXT Source 530 / i7-3770K / Corsair H100 / ASRock Z77 Extreme4 / SoundBlaster Recon3d
Samsung 850 PRO 512GB SSD/Seagate 1TB/2TB/WD 2TB
4x4GB Corsair Vengeance 2133 / PNY GTX 980 ti/ Seasonic M12II 850W