Hi , and thx for your answer.
Category Form was migrated.
I found a part of the problem.
This presta was a 1.7.3 upgrade to 1.7.6 and hookActionCategoryFormModifier was not in Db.
It was upgraded by Oneclick Module .
I had it and i can fix to the hook. But it doesn't work. I think another think is missing but what ...
Does anybody have an idea ?
Thx a lot.