Yes, it is working now.
This is my entry in ddns

config service ‘zzz’
option interface ‘wan’
option check_interval ‘10’
option check_unit ‘minutes’
option force_interval ‘60’
option force_unit ‘minutes’
option ip_url ‘http://checkip.dyndns.com
option ip_source ‘web’
option password ‘xxxx’
option username ‘yyyy’
option domain ‘zzz.dyndns.org
option param_enc ‘zzz’
option lookup_host ‘zzz.dyndns.org
option update_url ‘http://[USERNAME]:[PASSWORD]@members.dyndns.org/nic/updatesystem=dyndns&hostname=zzz.dyndns.org&myip=[IP]’
option enabled ‘1’
option service_name ‘dyn.com