Here was my issue. One of my WP site 123Takaful.com previously running on a shared host at Exabytes. Unfortunately the loading time for this site is unbearably slow. So I send email to support team who later asked me to disable the wp-cron. No , it did not worked out.
So I decided to move to Google Cloud Platform. Moving out a site was pretty easy, copy the files and copy the database. But I have problem with permalinks of my entries. It said the URL requested was not found on this server.
So Google gave me this answer, and you might to try it too:-
sudo nano /etc/apache2/apache2.conf
Options Indexes FollowSymLinks
AllowOverride ALL <----(edit from none) Require all granted
Then restart apache. It’s just working fine now.