If you’ve followed the upgrade procedure (https://www.advancedcustomfields.com/resources/upgrading-v4-v5/) correctly and you’re having problems then you should open a new support ticket https://support.advancedcustomfields.com/new-ticket/.
I should also say that I thing the steps are missing one. If I’m not mistaken the last time I did this I went through the database upgrade before I deactivated ACF4, but the last time I did this was a long time ago.
