I recommend you to check your .htaccess file.
Check your PHP memory limit; memory should be 64MB or above.
you can try increasing Memory limit by adding define ('WP_MEMORY_LIMIT', '128M'); in wp-config.php file.
To troubleshoot WordPress errors, you require to enable WordPress Debug, which can be done using wp-config.php.
You need to copy and paste the code in wp-config.php file shown below.
define( 'WP_DEBUG', true ); .
