I can't record the samplers (DDJ 400)

The SAVE button is to save the sampler patterns, not the samples themselves.

Okay and how do record my samplers for future use?

(I bought the DDJ400 above all to be able to use the software, I notice now that there are limitations in version 6, both in the samplers and in the FX effects)

I want to make sure you understand the difference - any version can keep your samples.

The locked save button is only for saving a recorded sequence of playbacks (think of it as if you were using the samples to create a song - that recording of sample triggers would be what's saved / recorded). The samples themselves stay in the sampler or in the Samples section of your tree to be recalled again later.