If it’s some sort of address issue , TT still managed to raise an order with OR , so they must have navigated the address issue successfully, it’s possible ( but not that likely ) that TT have the necessary ‘cable links’ between the OR ‘headend’ and TT backhaul network, but BT ( via BTw ) do not currently have their own cable links between the headend and BT/BTw backhaul, although in those cases it should show as FTTP unavailable rather than not showing any FTTP, but may explain why BT currently cannot offer service, you could try ( obviously with no commitment to sign up ) some other ISP’s that use different backhaul providers, like Zen or Andrews and Arnold .
As already suggested, call the BT FTTP customer service reps , they are much more likely to be ‘Au fait’ with issues like this , and if it is an address issue potentially can sort that out .
As stated, if you get regular customer service, keep trying until you get the FTTP team.
