[TYPO3-english] lightbox falis

[Peder Høy Kristensen]

Hi,
I created a new typo3 ver 7.6.18 (php ver 5.6) website and I wanted, as usual, to have a lightbox for enlarging images. First I tried t3colorbox and then jh_magnificpopup. Both extensions work excellent on other websites, but on my new website none of them work. When I click an image, it just displays the image in the browser window, not in a popup window as usual.
What could I possibly have forgotten in settings?

Best regards
Peder