If any mysterious error occuring on your WordPress site or getting just a blank white page first enable error reporting to see what error message appearing on that page.
How To Enable Error Reporting
Open your wp-config.php file and paste below code just after 1st line <?php
error_reporting(E_ALL); ini_set('display_errors', 1);
Now add below code above /* That’s all, stop editing! Happy blogging. */
define( 'WP_DEBUG', true);
Upload newly edited wp-config.php file then go back to the page where your error happening, now you can see what error messaging saying.