Windows 10 Enterprise: 

CKFK9-QNGF2-D34FM-99QX2-8XC4K

Windows  10 Serial Key: 

NKJFK-GPHP7-G8C3J-P6JXR-HQRJR

Windows  10 Serial Key Technical Preview for Consumer: 

334NH-RXG76-64THK-C7CKG-D3VPT

Technical Preview for Enterprise: 

PBHCJ-Q2NYD-2PX34-T2TD6-233PK

Windows 10 Home: 

KTNPV-KTRK4-3RRR8-39X6W-W44T3

Windows 10 Pro: 

8N67H-M3CY9-QT7C4-2TR7M-TXYCV

If none works then try – 

VK7JG-NPHTM-C97JM-9MPGT-3V66T