Hi Joomla works,
I am using Joomla 3.6.5. I have some kind of a conflict going on between reCaptcha and K2. I installed K2 a few weeks ago, found I was getting a lot of spam user registrations, so added reCaptcha as a plugin. I followed all the steps in this post to activate reCaptcha: www.pictordesign.com/whmcs/knowledgebase.php?action=displayarticle&id=136 . Namely:
Goto www.google.com/recaptcha and get your Public Key and Private Keys.
- Goto Joomla Admin > Plug-in Manager > Captcha - ReCaptcha and enter your Keys and ENABLE Plug-in.
- Goto Joomla Admin > Global Configuration > Default Captcha and set it to use "Captcha - ReCaptcha".
- Goto Joomla Admin > Components > K2 > Parameters > Comments > Anti-spam protection and set it to use "Google reCaptcha" (or Both), plus ENABLE "reCaptcha for registered users".
- Goto Joomla Admin > Components > K2 > Parameters > Advanced > down to "Anti-spam Settings" and enter your Keys again, plus set "Enable reCaptcha on registration form" to YES.
- Goto Joomla Admin > User Manager > Options (button) > Captcha and set it to use "NONE". This will turn-off the default user registration reCaptcha loading in the background behind K2 and causing the conflict.

But when I try to post a test comment I get the message: 'Could not verify that you are not a robot.'
I tried installing Aimy Capture-less form guard as an alternative but that didn't seem to be stopping spam registrations, so I have disabled it.
This is my site: www.alisonlloyd.com.au/index.php/about-alison-lloyd/alisons-blog
Can you please tell me what I should do?

Can you try disabling the reCaptcha plugin?

OK I have done that. Comments are now getting through to be moderated at the backend, which is nice. But I am back at square one because I am still getting dozens of spam user registrations each day. I have enabled Aimy Capture-less form guard, and I have switched 'enable k2 registrations' to 'No', but the problem persists. Further suggestions?

Yes, if you are using reCaptcha (in K2's settings enable them for the registration view) and you are still getting spammers, then you need to enable the stop forum spam integration as well.

Finally, make sure that you don't have any issues with your template overrides (deprecated code which prevents captcha from showing up).

I did the same actions. But I have the same sitution, in my K2 item, when you try comment my post.
You can check it here:
goldenscrew.net/%D0%B1%D0%BB%D0%BE%D0%B3/idei/dzhinsy-s-molniei-na-perednih-karmanah-vynimat-telefon-sidya-stant-proshe

Screenshot is here: imgur.com/a/MTl9t

I want to use recaptcha

Hello,
There is a JS error, most likely from your template jmp.sh/TiC0XLQ
Can you try asking your template's developer about this issue?

Krikor wrote: Hello,
There is a JS error, most likely from your template jmp.sh/TiC0XLQ
Can you try asking your template's developer about this issue?

No, this error not from template, because I setup another standart template and I had same error.
I agree, that template doesn't wok with this error correctly and redirect to index.php, but it is not error from template. :(

That JS error is coming from a K2 file which is not the same as the default one:

Code that produces the error:
<script type="text/javascript">window.addEvent('load',function(){(function(){if(document.id('fb-auth')==null){var root=document.createElement('div');root.id='fb-root';$$('.itemFacebookButton')[0].appendChild(root);(function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(d.getElementById(id)){return;}
js=d.createElement(s);js.id=id;js.src="//connect.facebook.net/en_US/all.js#xfbml=1";fjs.parentNode.insertBefore(js,fjs);}(document,'script','facebook-jssdk'));}}());});</script>

github.com/getk2/k2/blob/master/components/com_k2/templates/default/item.php#L321

A JS error can and will break K2's AJAX functionality.

Same problem!

Joomla 3.8.12
K2 2.8.0

Tried disabling Recaptcha plugin
Tried disabling JCH Optimize
Tried switching to Beez3 template
Tried disabling Akeeba admin tools
Tried reverting to default htaccess file
Tried disabling com_k2 template overrides

No luck! The recaptcha keys work fine with the Joomla registration form and the core Recaptcha plugin. Why doesn't K2 just use the built in Joomla / Recaptcha plugin type?

Also seeing these errors in the console:

VM36:1 Uncaught DOMException: Blocked a frame with origin "www.google.com" from accessing a cross-origin frame.
at <anonymous>:1:16
(anonymous) @ VM36:1
VM165:1 Uncaught DOMException: Blocked a frame with origin "www.google.com" from accessing a cross-origin frame.

But I've never had to mess around with "allowing" headers from a cross-origin site on any of my other Joomla / K2 powered sites. Comments are working on those sites just fine. Strange...