If you are eligible and can't claim, then quickest way is to just call BT on 0800 800 150.
See here: https://care.bt.com/claim_reward_card
Take it that you have read through the page linked below as it will be a virtual Reward card that will be sent to the email you have registered on your BT account.
Want to claim your BT Reward Card or Gift?
If you ordered Broadband:
You can claim online by logging into My BT using your BT ID. You can claim once you’ve received your order confirmation email.
If you ordered Broadband:
Once you’ve claimed, your gift will be sent at least 14 days after your service has been activated.
If you’re an existing customer:
You don’t need to do anything, as your gift will be automatically sent. If you ordered Broadband, this will happen at least 14 days after your service is activated.
A search for previous posts in the forum about this will bring up many, like the one linked below.
Can't claim BT Reward Card
You will see that they recommend phoning the helpdesk too on on 0330 1234 150, however I would use the freephone 0800 number.
I do not subscribe, so please do not always expect a reply.
