I discovered the problem.
Rather than what you have in functions php to this.
add_action('init', 'load_my_acf_field_group');
function load_my_acf_field_group() {
if (function_exists('register_field_group')) {
// register your field group
}
}
The problem is that loading of the text domain does not happen until after function.php is loaded so the translation does not exist when the field group is being created.