Your registration is working perfectly fine. What is not working is the 3rd party module (CB S5 Register - mod_cbregistration) you're using to render registration in a module. Please folks this is extremely misleading for our users when an issue is reported and you're not using CB as its designed. We do not support registration in a module, period.
Navigate to the below link (append your site) and you'll see registration works fine. I've confirmed this with "demouser1", which you can see from backend (delete as necessary).
index.php?option=com_comprofiler&task=registers
If the above link (append your site) DOES NOT WORK then there is a problem. If you use a 3rd party module and render registration in that module and it does not work then contact the developer of that module, not us.