If you did not change too much the custom menu is used if the menu manager is enabled. The question is: Do you have a menu set named "zenpage". If not it is quite normal that nothing is shown.

A new day, a new problem.
I showed the site to my mom yesterday and she told me the link under "pagina's" isn't there.
It is with me (logged in as admin) and it's working like it's supposed to.
The link is to a zenpage "werkbeschrijvingen", I'm using the zenpage menuset (I noticed there are no blue circles showing up next to the menu items).
It looks like another menuset (effervescene) is active, but I can't change it back to the zenpage menuset.

I upgraded to the latest build this morning and it doesn't solve the problem.

http://www.atelieranniec.nl/zenphoto/

Make sure the pages are published. If not only the loggedin admin with the rights to see them will see them.

They are published, the green symbol is next to the items in the zenpage menuset and I unpublished the ones in the other set. Still it isn't working.
The weird thing is, that is the only link that isn't showing.
Is deleting the effervescene set an option?

Note that the published status of an item is independent from the visible status in the menu. You can have a page published but set to invisible in the menu and vice versa.

Ok, how does that work?
Menulabel "Pages" is set to visible and so is the menufunction "all pages".
It should be showing up right?

Did you look at the pages tab?

I did, the green symbol for published is next to the page.
When I open the page the published checkbox is checked.
I know the page itself is on there, because my mom could get to it through the Tags.

Check the theme's sidebar.php page to see which menu set the custommenu function actually uses. Maybe you have indeed the wrong one.

if(function_exists('printCustomMenu') && getOption('zenpage_custommenu')) {
?>

This is the actual code.
And this one is for the pages:

acrylian said:If you did not change too much the custom menu is used if the menu manager is enabled. The question is: Do you have a menu set named "zenpage". If not it is quite normal that nothing is shown.

Menu manager is enabled, there is a menu set called "zenpage" (I'm trying to use that menu set, but it looks like it's not loading) and the only thing I changed is I have taken out the news page section.

Try to delete that menu set and recreate it by adding the pages manually. Might be that something has been screwed up as the theme tries to create a default menu set automatically on the first use.

Alternatively you could disable the menu manager so you use the standard menu functions.

I tried your last suggestion, disabeling the menu manager, but the link still didn't show.
I'm going to try the other suggestion.

I think I'm finally getting somewhere. Deleting and starting over seems to do the trick.
Thanks for your patience and your help acrylian.