@Milesh On the main router DHCP Server set Primary DNS: 8.8.8.8 , Secondary DNS: 1.1.1.1 Keep the connection: main router LAN port => AP router WAN port Test again.

@ECKS Move the ethernet cable to another LAN port of the modem or if that doesn't improve things, change the ethernet cable (use Cat 5E or Cat 6) and test again.

@Milesh This FW version (1.1.4) has been published for the US region since the beginning of November last year. I presume it's not much different than the same FW release for the EU region. Can you...

@rariyuda Yes, it is - check this FAQ and you'll understand why.

@IvanD Still that proves nothing definitively. I would have excluded a FW issue from the very beginning. You could email to support.forum@tp-link.com to ask for further suggestions and help.

@IvanD Uploading third party SW on your device will void the waranty, but since your device is not under waranty there's no need to worry about that. But if you haven't done this before there's a...