Wordpress – Set your wp-config.php to writable

 

A definition of a siteurl or homeurl was detected in your wp-config.php, but the file is not writable.
Set your wp-config.php to writable and reload this page.

WordPress of Bitnami 

WordPress of Bitnami when use SSL plugin, You can show this error.

So, Im recommend to connect SSH that server.
You should run the following command within ssh

sudo chmod 664 /opt/bitnami/apps/wordpress/htdocs/wp-config.php 
sudo /opt/bitnami/ctlscript.sh restart apache

Then You don’t show that error.