Cannot Register to default Membership

I have added default membership on my website using Membership Pro2 plugin

and i used this shortcode on registeration page

[ms-membership-register-user membership_id="389" title=""]

i tried to register 10 time but it always show this message

Sorry, your signup request has failed. Try again.

Here is link to register page:-
http://dnsct.com/ctreia1/register/

Please help me asap