OK, you have the only 90mm lens which is a little complicated to manage... is a collapsible lens, and you must EXTRACT it to be able to focus; to be precise, extract and turn it to secure the lens "tube", and you must do this with the lens at infinity (button "locked"). When the lens is correctly extracted, you can push the button and freely focus it as usual. The lens extracted is like this :
elmar-90_collapsible.jpg
The same applies when you want to collapse the lens : must be set at infinity, button "clickes", ok to turn & collapse the tube.