BuddyPress.org

The registration process on my website is not working.
wordpress 4.4.1
buddypress 1.3.3
http://www.pandadar.com

After I have filled the form and submit the application, it redirect to Home page without showing a sucessful and check email message. At the back end, there is no record (the user name not showing up in ‘pending’ or ‘Manage Signup’) of this application. The user did not get activation email either.

This is what I have done.
1. I disabled all the plugin including bp and use a 2015 theme.
Wordpress registration and activation works well.
2. I activate bbpress plugin, and it still worked.
3. I activate buddypress. Registration is in Register Page, and I can not register any more (and there is no error message in SCRIPT_DEBUG). I am redirected to Home after Submit.
4. I edit Setting>General, change it to ip address, remove www or add www back, it does stop to redirect to Home without www. But login wise, it is no help.

5. I set the permalink to post name and nothing changes.
6. I disabled all the redirect in the settings I can find in the dashboard, nothing changes.

I notice the action field of signup_form is empty. but it comes with the theme. I do not think it is relavant.

Does anyone what problem it is? And if i have to look into the code, where should I start?

Many Thanks!