Telephone line or Fibre optic link is connected to the openreach supplied modem for internet access? Without a router, you can access internet directly or not? If it is fibre optic link, you have to...

Who is your ISP? Another one is the same model or a different one from your ISP? You may go to Network---DSL Settings and try to change DSL modulation type to ADSL2 or G.DMT to see if it works.

1. What's the IP address obtained on HP laptop? How about the signal strength on the laptop? Can you log in web inerface of W9980? 2. To detect 5GHz Wi-Fi, you have to ensure that wireless network...

Did you try to contact TP-LINK support team? support.de@tp-link.com or http://ticket.tp-link.com/index.php?/Tickets/Submit

Can you provide a screenshot of dropdown menu of wireless 2.4GHz? As I checked the emualtor, there is wireless mac filtering option. But not sure if it is the same as your configuration page as maybe...

It depends on the modem.