Problem Setup (2nd)additional Wireless N300 router, TM Unified Modem

Hi guys,

Please I need helps .

Currently I'm using unifi modem with wireless router(Dlink dir-615) from TM. It is working fine.
Now I pull another LAN cable from Dlink dir-615 that connect with LAN port 2 to downstairs living room.
I connect this cable to my another wireless router DLINK Wireless N300 router.
but it could not work.

any clue. I did something wrong ?