Signin code

I’m using a page where I have the signin code as:

[sendpress-signup firstname_label=’First Name’ lastname_label=’Last Name’ email_label=’E-Mail’ listids=’141′ display_firstname=’true’ display_lastname=’false’ label_display=’false’ desc= ” label_width=100 thank_you=’Thank you for subscribing!’ button_text=’Subscribe’]

The list 141 is public. However, whenever the form is submitted, nothing happens besides the form page refreshes itself, no user is added to the list. Do you know what’s wrong?

http://ww.wp.xz.cn/extend/plugins/sendpress/