Maybe it can be blamed on something the Dark Apostle did after his experience with the interdiction of Etterdam. Something he did to Nysegard only because of its importance to the Stormlords, that lasted until his death 1000 years ago. Being cut off for so long no one caught it or tried to get links back up.
Could have been part of his experiments with cutting off the outer planes, make the block effective for the local planes and abyss, and blame any success with the outer planes on Sentir Fallon. The block for the Abyss and local planes lasting, but the block on the outer planes something that has to be channeled, like what Exador is doing right now.