Hi @iamntz
You need to upgrade ACF 3 to ACF 4 first before upgrading it to ACF 5. To upgrade ACF 3 to ACF 4, kindly check this page: https://www.advancedcustomfields.com/resources/migrating-from-v3-to-v4/.
To upgrade ACF 4 to ACF 5, kindly visit this page: https://www.advancedcustomfields.com/resources/upgrading-v4-v5/.
Also, please make sure that the database upgrade is successful.
Hope this helps 🙂
