Zombie spawner not spawning.

Im playing in a world on xbox 1 and the zombie spawner has stoped spawning. I saw a zombie Villager instad of the nirmal zombie slinning in the block and have watched ot tun back to a normal zombie but not start spawning again.

I have tried to reset the block but its not fixing it.

I also checked my other two spider spawners and they are not working either.

Please provide a fix!!!