Demo Import Fails: “Sorry but your import failed.”
If you get this error, most likely the importer can not work with your webhost.
You might want to try asking your webhost to increase max_execution_time (or any other webserver timeout to at least 300 secs) and memory_limit (to at least 196M).
Another thing which might solve the issue is to increase WordPress memory limit setting. Add below code to your wp-config.php before importing
demo content.define(‘WP_MEMORY_LIMIT’, ‘500M’);
define( ‘WP_MAX_MEMORY_LIMIT’, ‘500M’ );
Basically, If the limits on your server settings are very low then the content will not import.