Blaze spawners won't work

My launcher says I'm in v1.20.32 but the site won't let me enter that

In a 2 player realm a blaze spawner doesn't spawn any blazes. 
I tried all difficulties but that didn't change anything. The spawner is active and the player stands less than 5 blocks away from the spawner. In the rest of the fortress blazes spawn naturally, as well as other mobs