SSL installed on Apache2 but HTTPS not working
In httpd-ssl.conf, do you have Listen 443
If not, try adding that, and restarting apache.
First check if mod_ssl is enabled. If not, enable it by running a2enmod ssl. Then check if Apache is listening on port 443 for https. Then check if the firewall is not blocking port 443.
If anyone else finds this and is using Amazon Lightsail (like me), you have to use their web UI to explicitly open port 443.
I spent hours pouring over my server config files before I discovered that :/