The fields were loaded, but not the editor / datepickers…
but after being in contact with the Support…
we found the solution …
Somehow the the difference between 2.5.6 and 2.6.9, wouldnt load the js, if acf_form() is added directly (in my case) in the top of my index.php, but if the get_header hook was used it worked with the newest version
I have now tried downgrading fra 5.9 to 5.6 version of ACF… and now it works, but i don’t see this as a viable solution to my problem for the future