My server does not change the world

I have a problem with the world of my pmmp server, what happens is that I try to change the seed of my server and as much as I try the world remains the same, the seed changes, but the world does not, in this world it will not be generated mobs, rivers, flowers, fish, algae,

I have the following plugins installed

Purechat

Pureperms

Freeze

CustomAreas

Lockmystuff

And it is not possible to active the mob generation and change the world