Could you please give us more information about what are you trying to achieve? The guide you linked is related to generate a new SSL certificate, but it seems you are having issues with VirtualHosts configuration.
Apart from that, according to the error message you posted, you are trying to include a file that doesn't exist. Could you please check the
/opt/bitnami/apache2/conf/bitnami/bitnami-apps-vhosts.conf and ensure that the path to the included
http-vhosts.conf file is ok?
We have a Support Tool that will gather relevant information for us to analyze your configuration and logs. Could you please download and execute it on the machine where the stack is running by following the steps described in the guide below?
How to Run the Bitnami Support Tool
Please note that you need to paste the code outputted by the tool in your reply.
Hope it helps,