I have many sites and subdomains running with K2 on J2.5.
Just started using 3.3 and am having a problem with overrides.
I have created the files as I used to.
I can see the override templates in the backend - ie I can assign them to categories.
But the front end does not show them.
My experimental site is here: icss.icmconferences.co.uk/
Template is Artisteer generated some minor mods.

The overriding process is the same in both Joomla! versions.
Can you try the same process with another template?

I have done, I downloaded purity iii from JoomlArt to test exactly that.
I cannot see what I am doing wrong. I have revisted the various guides listed in this forum but I cannot work it out.
I know it has to be a stupid mistake but...

Now tried with Takai template - still no joy...

Hello,
Please read this post www.joomlaworks.net/blog/item/194-k2-inheritance-sub-templating .

If you are following this method then some extension is blocking the default overriding procedure. Disable extensions one by one in order to find the culprit.