advanced custom field does not return field value

I installed the plugin on my site, but I can’t use it. I’ve used the_field (), get_field () and it doesn’t return any value. I used get_post_custom_values (“”) but in fields like image does not work, always returns an empty field. Is there any configuration in the functions.php or wp-config.php file that you have to do? I’ve searched in several places, but I can’t find a solution. I’m desperate for this !!!!!
Here’s how I’m using it on the page:
” alt = “Image” class = “img-fluid”>