I had issues when installing and activating a particular WordPress plugin called ‘ToolSet Types’.  After activating the plugin I will get a Page not found. I couldn’t access the wp-admin site but the blog remained active.

To get back the blog as it was one can browse the site using FTP and delete the particular plugin folder under /wp-content/plugins. This will make the wp-admin accessible again.

After some research I found out that the issue could be the memory setting on the WordPress wp-config.php file which is situated in the root WordPress folder. To fix this, open the file and add the below lines.

/** Memory Limit */
define('WP_MEMORY_LIMIT', '256M');
define( 'WP_MAX_MEMORY_LIMIT', '256M' );

In my case, after adding the above lines, refreshing the WordPress page I was able to install and activate the plugin.

Hope it helps with other plugins thou I encountered this issue only with the ToolSet Types plugin.