For anyone that encounters the same problem.. the reason that this happens is due to changes made to .htaccess.
To roll back changes, delete the plugin from its folder and then replace the code in .htaccess (in the main website folder) to this:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
