Hi,
It is not possible to tell what caused your problem with the given information. It could be the memory limitation set by your server, a conflict with other plugins or theme, PHP errors, missing files etc.
Why don’t you try providing any errors you see to help others to detect the cause of your problem? If you are not familiar with getting PHP error log, the following steps will help.
1. Find wp-config.php
in your WordPress installation directory and open it.
2. Find a line that is similar to define( 'WP_DEBUG', false );
3. Replace it with
define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );
and save the file.
4. Activate the plugin and open the wp-content
directory. A log file should be created. Then post the log.
5. To restore the change, revert the change made in step 3.
This page may help as well.