There are many reasons which can result the error of K2 Component in Menu items list as component com_k2 does not exist and there are many solutions on the net but here I want to discuss one solution which I could not find on the net.
After migration from Joomla 1.5 to Joomla 2.5, you can encounter the same error in menu items.
At front end you may see below message on clicking on any menu item.
When you enter your login credentials, you face a new error
Solution is very simple for novice persons. Go to menu items list on backend administrator and click on menu item which is facing such issue. Now click on Select button.
Then select menu item preference as per your requirement, Save and exit.
Now, go to K2 categories and open the same category which was selected on above step and set its access level to Public as shown below. Save & close.
Still, may you face below error.
Its mean, you have to set access level of your articles. Go to articles resides in the same category, open an article and set its level to public as:
That's all, you have done. Now you will see your categories with their articles on clicking to menu item.