by Mohammed Essaid MEZERREG.
Perhaps you should check if they still enabled along with the related configurations like the authenticated users, tokens, protocols, .. etc.
And if everything is good, I think you should check the functions you are using, are they still there, because some functions are deleted from the webservices like core_user_get_users_by_id (this I know about) and they added additional services too, so maybe your client is outdated by the new upgrade. You check the list of functions in this page http://yourmoodleurl/admin/webservice/documentation.php or you can go to site administration > plugins > webservices > API Documentation