Could you show us the contents of that directory and the
ls -la /opt/bitnami/apps/wordpress
ls -la /opt/bitnami/apps/wordpress/htdocs
ls -la /opt/bitnami/apps/wordpress/conf
It is really weird, since
bnconfig should be included. I just tried it on a GCE image and it worked for me.
Just to get more information, is it launched from the Bitnami GCE LaunchPad or installed via a Bitnami installer? In the second case, maybe it might happen because the installation did not finish properly.