[erlang-questions] Newbie problem with snmpm

[Magicloud Magiclouds]

Hi,
    I am new to Erlang. While I was learning to use snmp, I got some 
problems.
    I used snmp:config() to make all the configuration files (only 
manager, no agent). Then
# erl -config sys.config
 > application:start(snmp).
ok
 > snmpm:which_users().
[magicloud]
 > snmpm:g("magicloud", {10, 9, 81, 11}, [[1, 3, 6, 1, 4, 1, 388, 6, 2, 
10, 1, 29]]).
{error,not_found}
    I am sure that the ip and the OID are correct. So what does 
"not_found" mean?

Thanks.