Requirements

The WP Post Map plugin is made to work with WordPress 3.5 or newer, PHP 5.6 or newer, and MySQL 5 or newer. However, we recommend you follow the requirements listed for WordPress.

PHP Configuration

Many issues can be caused by PHP configuration settings that are too low. Issues such as: having problems uploading or installing files, experiencing a white screen when trying to access your site, mysteriously losing menu items when editing large menus, etc. can all be related to PHP configuration settings.

Recommended Settings
max_execution_time180
memory_limit128M
post_max_size32M
upload_max_filesize32M

If you are unsure how to change these settings yourself, your hosting company can help. You can see what your current settings are by using the following plugin:

https://wordpress.org/plugins/wordpress-php-info/