I am having problem with getting K2 registrations working, only when the K2 User profile is disabled is when the normal Joomla! 3 registration will work.

Once it is enabled after the registration is finished, no email is generated, no confirmation and it will redirect back to the front page main site.

Can someone give me some advice on how to get it working.

I am using version- 2.6.7 K2.

Please update to K2 2.6.9 which currently the latest version.
Let me know if the issue persists.

After the upgrade the problem is still there. What else can do I do?

The K2 User profile will show the author's extended information. It does not intervene with registrations.

Are you using any 3rd party K2 plugins? Are you using Joomla!'s or K2's default registration?

I'm using joomla user XTD with it which I also have disabled to have it have it as default as possible. I'm using AllVideos (plugin) as third part extension.

user XTD from what I can see is on beta and they devs say not to use it on production sites.
Is it possible to remove this extension completely and try again?
Also are all of K2's plugins enabled?

I have completely removed all the UserXTD extension. Disabled Acymailing extension plugin and disabled the allvideos K2 plugin. Still it is not working.

Can you PM your details if you are interested in doing some consultancy work?

Try the following:
Reinstall K2,
Use another template to make sure that this is not a template issue.

I have tried to install a new template with a reinstall of the K2 component. It still is not working. All I am getting is no error message and redirecting back to the front page.

The backend administrator works to add the user to the CMS.

As soon as I disable the K2 user profile then it work.

Any other suggestions?

Try to reorder the plugins.
Make sure that the K2 User plugin is located at the end of the list.

Finally you can also try the dev version. You can get it from here: getk2.org/assets/get/