The noiseSeed() function only works once, and only if called before noise().  It will not RE-seed the perlin noise routines once they'be been seeded.  I believe the problem is the internal perlin[] array that only gets created once, but should probably be repopulated from scratch whenever noiseSeed() is called.

To demonstrate, run this sketch and note seed 0 value:

noiseSeed(0); // make a rng with seed 0
noise(0,0,0); // fill perlin[] with seed 0
println(noise(0,0,0)); // prints 0.6852823

Then run this sketch and note seed 12345 value:

noiseSeed(12345); // make a rng with seed 12345
noise(0,0,0); // fill perlin[] with seed 12345
println(noise(0,0,0)); // prints 0.33919036

Then run this sketch and note that seed 12345 returns seed 0's value:

noiseSeed(0); // make a rng with seed 0
noise(0,0,0); // fill perlin[] with seed 0
noiseSeed(12345); // make a rng with seed 12345
noise(0,0,0); // does not repopulate perlin[], still from seed 0
println(noise(0,0,0)); // prints 0.6852823