Web service error

Hi,

We are running a Moodle version 383 in a Ubuntu Linux server. When I was trying to call this function: core_enrol_get_enrolled_users

from the web service, I am getting this error:

{"exception":"moodle_exception","errorcode":"errorcoursecontextnotvalid","message":"You cannot execute functions in the course context

(course id:157). The context error message was: Site policy not agreed: <a href=\"https:\/\/lms.rcmstg.com\/lms\/admin\/tool\/policy\/index.php\">Click here to open the site policy.<\/a>"}

Can somebody give me some clues, please?

Thanks for your help,

Carlos