Blaze Spawner Not Working

So for some reason our blaze spawner on our realm stops working. I've built a farm around it and it will work when we re upload the world then if you walk away it stops working. But it worked great on a friend's realm of mine and now it's not working at all so I don't know why it keeps stopping. I can't find any other spawners. I don't know if it's an issue with something I built or what. But even if I remove something it still doesn't start working again. I don't know if the Redstone is too bright now or what.