@ddanova
Don’t know exactly what the problem was but this finally works:
if( function_exists('acf_add_options_page') ) {
$page = acf_add_options_page(array(
'page_title' => __('My Theme Options', 'productify'),
'menu_title' => __('My Theme', 'productify'),
'menu_slug' => 'my-theme-options',
'capability' => 'edit_posts',
'redirect' => false
));
}