The reason for this is that the field keys of the fields you created on the new site do not match the field keys of the old site. The field key references for the ACF fields will have values from the old site.
You have a some choices.
You can export the field groups from the original site and import them to acf instead of recreating them. This will ensure the field key references remain the same.
You can use an export/import tool that is ACF aware like https://www.wpallimport.com/
