Setup SSL for Port 443 Access (Raspberry Pi 3)

Nextcloud 12.0.4
Operating System Raspbian Stretch
Apache 2.4.25
PHP 7.0.19-1

I setup my RPi3 with Nextcloud via these instructions:
Basically everything is working aside from the external connection. I have to try to access Nextcloud via SSL because my isp blocks 80, but not 443, anyway when I try to access https://IP/nextcloud this happens:
This site can’t provide a secure connection
IP sent an invalid response

Anyone run into this? I’ve followed all the steps given by Pi My Life Up including the SSL portion, but I just can’t get it working… Is there maybe something I’m missing? Or possibly because port 80 is closed?