Increasing Memory Limit To PHP
Some servers (usually shared hosting plans) have a very low PHP memory limit by default.
Low PHP memory limit can cause a blank screen (also know as the white screen of death), including other errors on your website. Luckily, increasing the PHP memory limit is a very simple task and can be done with a small tweak in your wp-config.php file.
Have a look below at how to increase your memory limit or read the documentation on WordPress CODEX.
Increasing the Memory Limit
Open your wp-config.php file via FTP and add the following code right above the last line says "That’s all, stop editing! Happy blogging":
define( 'WP_MEMORY_LIMIT', '512M' );
You can alter the 512MB to any value you want, but 512MB should work pretty well for most live sites.
Note: Whether or not you will be able to alter the wp-config.php file on your own depends on your hosting provider.
If you are unsure on how to increase PHP memory limit and whether or not you have the permission to do that, please contact your hosting provider for detailed information and/or help.