After updating to latest WordPress version 5.9 it can happen that you get a blank white page or a fatal error saying something like:
[26-Jan-2022 15:52:28 UTC] PHP Fatal error: Uncaught Error: Call to undefined function get_allowed_block_template_part_areas() in /home/web/public_html/new/wp-includes/blocks/template-part.php:168
If you only get a white page without seeing anything, you can verify this error by activating the WordPress debug.log.
When this error happens it means the WordPress automatic went wrong and broke your WordPress installation.
To fix that error follow the steps below:
- Download WordPress 5.9 core
- Extra the zip file
- Upload only the folders “wp-admin” and “wp-include” via FTP to your website. Overwrite the existing files from that folder