I have installed K2, imported my existing joomla articles, set up various k2 menu items but none of them are displaying any content. The category titles are appearing but the pages are blank. Not sure what step I may have missed.

Try creating a new k2 category
add an item to the new category
make a menu link to it and see if it shows up
If it works compare the category settings to the imported category settings

thankyou but it turned out to be a sef conflict.

I'm having the same problem with item content not showing up from the menu links and it's not an SEF issue. I have other items under the same category but when I created a new item the content did not display when clicked from the menu link which is the only way to link to the content.