Hello to everyone and sorry if I have not been able to find the solution.

I have a problem by inserting an article via frontend.
The tabs above do not work and in fact, in console I see this error:
Uncaught TypeError: Cannot read property 'noConflict' of undefined
at k2.backend.js

at this line:
var $K2 = $.noConflict();

I've also tried disabling "JCH Optimize" and "jQuery Easy".
but the error remains.
Any suggestions?

Thank you,
Elisabetta

Hello Elisabetta,

jQuery is not being loaded in your site.
Is it enabled in K2's parameters?

Hi and thanks for reply.
My site loads jquery from Joomla framework while it is disabled in k2.
This is not a new site, exists since 2012 and has always worked. something changed after I updated Joomla and K2 a few months ago. Unfortunately I didn't have time to look at the problem right away.
However, thanks to your suggestion, I noticed that something changes in the popup that opens in front end to insert the article.
In the head doesn't load the same things that are on the pages:
like this google.load ("jquery", "1.6.1");
Can this help?
Thanks again

EDIT: I think the change is due to itemform.php that now points to the backend file in Administrator and so it is out of the frontend theme, isn't it?

Hi I have already tried (I've removed all k2 override) but the result does not change even allowing it to load the original file.
As I wrote, I see that the popup loses some lines of code in the head (probably also something jquery)

Which jQuery version is currently being loaded?
Is it loaded before all other scripts?

Hi, thanks for replay.

Here is what I have at this time on this popup:
imgur.com/a/4h1WC

while the frontend side is different: I've jQuery 1.12.4
It works all properly, even jquery and without console errors

It is normal not to load the entire site in the popup since a lot of the content is not needed.
Strange enough, the order is correct.
JQuery before all other scripts etc..

Can you try replacing that line with:

Thanks Krikor.
Ok, at least something change ...
I'm attaching the screenshot
imgur.com/f709a9Y

Yes, this means that the script is being executed.
Which version of Joomla! are you using, and can you share a screenshot of the order that the scripts are being loaded?