Hi @agon024
Have you upgraded your database? After you updated ACF to the PRO version, you should see a notice that asks you to upgrade your database. This page should give you more idea about it: https://www.advancedcustomfields.com/resources/upgrading-v4-v5/#after-you%20update.
Please don’t forget to backup your site and database first before doing it.
Thanks 🙂