I have just purchased a dev license for ACF pro and when I activate the plugin, it tells me I need to update the DB. I click to do this (after backing up my sql…) and it just hangs with the spinner, saying “Upgrading data to version 5.0.0”. Left it for 15 mins, no change… Any ideas?
This issue might result from a theme conflict, I would recommend you switch to one of the stock WP themes and try upgrading your database again.
Updating to 5.3.0+ should fix this issue. The hanging is probably due to an issue with validation_complete inside input.js.