@Alva1960
Are you sure that you are in "edit" mode on the BT Hub?
You said in an earlier post "I have done a full factory reset and changed the admin to a password I know".
Why did you change the admin password at this stage? It shouldn't make a difference, but have you tried doing a factory reset and then making the "Plusnet" changes when logged in to the hub using its built in default password/
If that works, then change the admin password after that.