I had BT broadband installed 1/7/21 and had a text and email letting me know that I could claim the £100 reward, but when logged into the BT account, I have no reward available, nor one showing in the rewards history.
Welcome to the BT Community and thanks for your post!
I'm sorry that there isn't a reward showing on your profile when you log in to claim. I have sent you a private message with instructions on how you can send us over your details and we'll look into this for you. See: Private messages