Prestashop is a very useful e commerce software. One of the common errors while fresh installation or upgrade is a white screen. This is very disturbing to as there is no error message telling you what is wrong.
Mostly it is due to program running out of allowed memory as Prestashop 1.6 is a bit more memory intensive than previous versions. This article will show you how to update your server for memory_limit to fix the most common cause of the white screen error.
Check PHP memory_limit
<?php phpinfo(); ?>
How much memory do I need?
2. Your theme (some themes are well coded, some of them not. In addition, some themes use own customized modules, sometimes they affecting performance)
Increase PHP memory_limit
memory_limit = 128M ; /* Change the 128M to your needs */
Step 3: Restart Apache. Use follow command to restart apache：