It first started after i set https://(My_Domain_Name).com into Configuration > Web > Base URLs & Base URLs (Secure) > Base URL for Static View Files & Secure Base URL for Static View Files (I'm not even sure if this is the cause). I tried several solutions including: (Solutions from similar problems in stackexchange)
1) Go to pub/static folder and remove everything, except .htaccess file. Open up app/etc/di.xml find the path Magento\Framework\App\View\Asset\MaterializationStrategy\Symlink and replace to Magento\Framework\App\View\Asset\MaterializationStrategy\Copy. (It is already set to Magento\Framework\App\View\Asset\MaterializationStrategy\Copy by default)
2) Using Putty to run below commands
bin/magento setup:static-content:upgrade bin/magento setup:static-content:deploy bin/magento indexer:reindex
3) Using Putty to run below commands
php -dmemory_limit=1G bin/magento setup:upgrade php -dmemory_limit=1G bin/magento setup:di:compile php -dmemory_limit=1G bin/magento setup:static-content:deploy -f php bin/magento cache:clean
4) The permission for /pub/ and /var/ folders is set to 0755 as per default.