Have noticed a few posts over the years on this subject, and I am suffering yet again with it.
Manage to watch a few minutes on my iPad, then the dreaded CN001 messsage. Only solution is to come out of BT Sport and log in again to get another few minutes of viewing. Haver managed to miss all of the goals in the first half of today's game, and missed all but on on the Conference game yesterday with the same problem.
I have deleted and re-uploaded the BT Sport App, but this makes no difference.
It's really becoming a joke now - I resigned up with BT to get BT Sport, but I seem to be able to watch is less than ever.