If your site show this error message, it means that your memory limit is not enough for running site now. You need increase your memory_limit again.
If you run your site in localhost, you can go to your PHP.ini file (usually in xampp\php\PHP.ini) and change memory_limit like that:
After you changed in PHP.ini file, please try re-start your Apache again.
If you already uploaded your site to live host, you should contact with hosting provider to increase your memory_limit. They will support for you.
Hope it is helpful for you.