my friend and i had the same problem, we had no idea what the problem was, however our server was lagging, we removed a few modes and after removing extra biomes ruins and the battle towers mod all the meteors that should have fallen seemed to fall all at once, we believe it was the extra biomes mod that's causing the problem because we found out a battle tower also spawned after we removed the mod, and before we removed battle towers.
we're not sure if this conflicting mod problem is the cause but we think it most likely is. try removing the extra biomes mod just to see if the meteors fall. after harvesting the ore you can always re-add the mod for more biomes to spawn.
-good luck
--the mod might not be set to let meteors fall in biomes other than those indicated, which would cause a problem.