[SOLVED] Fatal error: Cannot declare class K2ModelItemlist

The Error:

Fatal error: Cannot declare class K2ModelItemlist, because the name is already in use in \components\com_k2\models\itemlist.php on line 977

How to fix:

Solution #1

Components > K2 > Parameters > SEO > Enable custom SEF settings for K2 URLs > No.

Solution #2

Edit the file: \components\com_k2\router.php

Comment the lines 28-29.

// require_once(JPATH_SITE.'/components/com_k2/models/itemlist.php');
// $itemlistModel = newK2ModelItemlist;<br>

P.S. This is a known issue by the K2 development team, that I have already reported it here https://github.com/getk2/k2/issues/526 and they will fix this on the next update release of K2.