Sometime configuring Apache2 for SSL it could return Internal Server Error.
If we look at error.log we have:
.htaccess: Invalid command 'RewriteEngine', perhaps misspelled or defined by a module not included in the server configuration
This message tell us that we don’t have the module Rewrite or the module is not enabled.
For solve this issue, we can simple do:
sudo a2enmod rewrite sudo /etc/init.d/apache2 restart