Fatal error: Allowed memory size of xxxxxxxx bytes exhausted.

You may need to set a higher memory limit for your WordPress site to avoid some of the most common errors. The default memory limit for WordPress is 32MB.

How To Increase The PHP Memory Limit For WordPress

Connect to your server via FTP and edit the wp-config.php file. Add the following line:
define('WP_MEMORY_LIMIT', '96M');
If the solution above won’t work in your case, then contacting the hosting company should solve it.

Read more about increasing the PHP memory in the WordPress Codex.