I use the JomLike (www.corephp.com) but in some items I can't see the like / dislike and in some others I can see.

 

As the corephp.com told me the like / dislike component works only if the onK2AfterDisplayContent is used on my template (which is custom). So can I insert the onK2AfterDisplayContent into the item.php?

Check out the item.php in the default folder. Search for onK2AfterDisplayContent. Copy the code into your override if its not there. I would be carefull about the order of the events and make it the same as in default/item.php

The solution was not to hard.

 

I hadn't enable the "" from the whole categories.

 

;)

""  ??

Enable K2 plugins