@AbdulAdil 

Is there any thing can be found on the controller log? Only the WAN down?

For PPPoE connection you can try to use a smaller MTU, like 1480 or 1460. 

Are you able to ping a public DNS when the Internet is not working?(like 8.8.8.8)

Try change the LAN DHCP primary DNS to 8.8.8.8 if you do have access to the DNS server

  Hi @Somnus 

Is there any thing can be found on the controller log? Only the WAN down?

Ans: There is nothing on the controller logs just that WAN is down.

For PPPoE connection you can try to use a smaller MTU, like 1480 or 1460. 

Ans: Will try the smaller MTU

Are you able to ping a public DNS when the Internet is not working?(like 8.8.8.8)

Try change the LAN DHCP primary DNS to 8.8.8.8 if you do have access to the DNS server

Is there any thing can be found on the controller log? Only the WAN down?

Ans: I did, but complete WAN was down, not able to ping any public ip or domain

Are you able to ping a public DNS when the Internet is not working?(like 8.8.8.8)

Try change the LAN DHCP primary DNS to 8.8.8.8 if you do have access to the DNS server

Ans: WAN gets disconnected

Thanks

  Hi @Somnus 

I have tried the settings which you have suggested lower MTU (1480 and 1460) but it gets disconnected.

Ping ip DNS/domain gives message as unreachable

Thanks

  @AbdulAdil 

It's hard to say, maybe compatible issue, maybe the router's issue. You can try to contact local tplink support and update result here.