Hello, i have fresh install of k2 version 2.7.0
And updated Joomla to version 3.6.2
My problem is that I cannot add tags or extra fields to articles as the javascript which gives options does not work.
In the extra fields selection the form field doesn't display at all.

I have the message at the top of the article:
Strict Standards: Only variables should be assigned by reference in /home/xxxxxxxxx/public_html/plugins/k2/extrafieldtab/elements/extrafields.php on line 31.

and this message at the top of 'Item view options in category listings'
Strict Standards: Declaration of K2Element::render() should be compatible with JFormField::render($layoutId, $data = Array) in /home/xxxxxxxxx/public_html/administrator/components/com_k2/elements/base.php on line 25

Could you please assist as there are many, many articles created in the K2 component all using tags and extra fields. This issue inhibits site functionality completely.

Hello, please update to 2.7.1 ( or 2.7.2 - github.com/getk2/k2 )

Also check the console tab of your browser's developers for any potential JS errors and report them here.

Finally in production websites you should disable error reporting in your site's global configuration.

Hello,
Have installed latest version of K2, (k2-2.7.1), but still get same strict standards message and tags/extrafields JS problem

I have checked browser console for JS errors which returned following...

JQMIGRATE: Migrate is installed, version 1.4.1
k2storejqui.js:16 Uncaught TypeError: this.element.uniqueId is not a function(…)
jquery.min.js:2 Uncaught Error: Syntax error, unrecognized expression: [href=#metadata](…)
jquery.min.js:2 Uncaught Error: Syntax error, unrecognized expression: [href=#itemViewOptions](…)
k2storejqui.js:16 Uncaught TypeError: Cannot read property 'element' of undefined(…)

The notices can be hidden by deactivating error reporting (which should be done in production sites). The upcoming version will take care of notices as well.

Now, from what I can see you are using K2Store which generating the JS issues which cause the tags and extrafields to fail.

You should c/p our conversation to the K2 devs regarding these issues.