D7, Bartik, live site
Everything worked until I tryed out some themes, then returned to the original, Bartik.

Trying to 'Add content' sends: 'You have not created any content types yet. Go to the content type creation page to add a new content type.'

In Admin>Structure>Content types there is a full list of all my content types.
In Content list, the type of content is still displayed as 'basic page' (which is what I have used so far).

So, everything is there, only 'Add content' can't see it.

It appears that through theme changes something that connects 'Add content' to content type has gone missing.

What connects 'add content to 'content types', where can I find these files and how can this be fixed?

Thanks