I have two enviroment: test and real-system.
In test I can create an user via web service like this: http://mydomain.example.com/webservice/rest/server.php?wstoken=MYTOKEN&wsfunction=core_user_create_users&users[0][username]=xxx&users[0][firstname]=yyy&users[0][lastname]=zzz&users[0][email]=mailuser@mailtest.com&users[0][password]=xxx&users[0][preferences][0][type]=auth_forcepasswordchange&users[0][preferences][0][value]=1
In test I haven't problems and I can see the user in Moodle.
But, in real-system, I can't creatr the user like this: http://realsystem.example.com/webservice/rest/server.php?wstoken=MYTOKEN&wsfunction=core_user_create_users&users[0][username]=xxx&users[0][firstname]=yyy&users[0][lastname]=zzz&users[0][email]=mailuser@mailrealsystem.com&users[0][password]=xxx&users[0][preferences][0][type]=auth_forcepasswordchange&users[0][preferences][0][value]=1
In real system I have this error:
<?xml version="1.0" encoding="UTF-8" ?>
<EXCEPTION class="invalid_parameter_exception">
<ERRORCODE>invalidparameter</ERRORCODE>
<MESSAGE> ... ... ... </MESSAGE>
</EXCEPTION>
Have you got an idea about this? Why in test I can create an user but not in real system?