Can you execute the following command in the LightSail instance and share the output with us?
After checking your configuration files, it seems that the
/opt/bitnami/apache2/conf/bitnami/bitnami.conf file was not properly modified. For example, at line 26, The
Listen 443 directive appears after some other directives, but it should start in a new line. That should be the cause of the issue.
Please, try to apply again the changes that @davidg suggested making sure that the final file looks like the one specified in the previous post and then restart the instance again.
Hope this solves the issue!