I would just copy the value straight out of the database, insert that value and see if it works. The actual value is an array that is serialized and base 64 encoded. /advanced-custom-fields-pro/pro/api/api-pro.php line 353.
Hoestly, if you are updating ACF on one site and then mirroring it to another site then there’s really no reason to have it activated on both sites. The only thing that activation gets you us updates, so you only need it it activated on the site where you’re doing updates.
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