It’s hared to answer, because you didn’t posted any details.

Once you add field ACF to the post it is visible for the plugin at the same name as defined in ACF.

Maybe you are using serialized value of field, try to follow this topic:
https://github.com/athlan/wordpress-custom-fields-permalink-plugin/issues/26

If you think there is an issue in plugin, please reproduce the bug, describe deeply and raise the ticket in github.