[MC-4478] Spawners not spawning

The spawners do not seem to be spawning any mobs. I have looked at both a zombie spawner and the skeleton spawner shown in the screenshot.

The spawners go through all the motions, The fire outside the spawner, but no mobs spawn.

Attachments

Are all the required spawning conditions met? (See algorithm here) Also, make sure your game is not set to peaceful.

Sorry for the false alarm... it was set to peaceful.
hangs head in shame
Thanks for the quick reply.

Don't worry about it. Despite false alarms and duplicates, the community's input is still very appreciated.