Update user data problem

by Mohammed Essaid MEZERREG.  

I am trying to use core_user_update_users function but I am getting this error with all users?

string(98) "{"exception":"moodle_exception","errorcode":"usernotfullysetup","message":"User not fully set-up"}"

array(1) {

  [0] =>

  string(98) "{"exception":"moodle_exception","errorcode":"usernotfullysetup","message":"User not fully set-up"}"

}

Is there special configuration of this function, I tried this with 5 servers and they all returned the same message?

The user of the external webservices has all capabilities and can do everything.