Hi @mb123
Thanks for reaching out to us.
If you connect a computer to the BT modem, can you access internet on the computer?
If you can, then please refer to this guide to copy the MAC address of this computer to the TP-Link router, then your Archer C6 can be recognized by the BT modem.
How do I configure MAC Address Clone on my TP-Link Archer Router?
If you can't access internet on that computer, I am afraid there is MAC binding on your ISP side and your ISP only binds the MAC address of bt hub2, so that both computer and TP-Link router can't be recognized. In that case, you need to contact your BT ISP to ask them bind the MAC address of your Archer C6.