<p>See our <a href="https://www.bt.com/help/broadband/bt-cloud/getting-set-up/download-or-access-files/how-do-i-download-files--folders-and-devices-from-bt-cloud-">help page</a> for further information.</p>
Where are you getting the warning, what is sending it to you. As far as I am aware if a sender is blocked BT do not tell you its blocked, it is just blocked!