Fatal error: Allowed memory size is showing if the default WordPress or hosting allocated memory is reach. In some case this can be fix via wp-config.php, php.ini, or .user.ini. If the error is still not fixed, better to contact your hosting provider and let them fix the error.
This is my error:
Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 32 bytes) in /home/site-folder/public_html/sample.com/wp-includes/meta.php on line 830
Using php.ini or .user.ini.
memory_limit = 512M;
Using `wp-config.php`.
define( 'WP_MEMORY_LIMIT', '512M' ); define( 'WP_MAX_MEMORY_LIMIT', '512M' );