ACF does work on mutlisite. There is not enough information in your question to figure out why it’s not working for you. The only thing that I can point you do is that you need to make sure that the code is being loaded and that the field group exists on the sub-site. Creating a field group on the main site does not automatically create the same field group on a sub site unless use PHP to register the group and that code is being loaded by the sub site.
