Dear @OPMASH,
ISP : TM UNFI (https://unifi.com.my) Malaysia
How to setup TM Unifi business to TL-ER6120?
To set up the Internet, please ensure that you can get an Internet connection from the ISP modem, or you need to set up the Internet connection on the ER6120 router with the information provided by your ISP.
On the ER6120 router side, we only need to connect the ISP modem (router) to the WAN port of the ER6120 via cable, then connect a PC to the LAN port of the ER6120 to set up the Internet connection by accessing the router page via http://192.168.0.1.
For further assistance, please kindly provide more details so that we can help you here.