Raspbian - Disabling SSL to Upgrade Owncloud

Hi everyone,
i have successfully installed owncloud on my Raspberry Pi 3 model B and i'm using it to test it's features as a home/family cloud server.
I have an issue tho : once configured SSL validation witn a self signed certificate i cannot launch the upgrade tool from the settings panel because because it pops "cURL error 60: SSL certificate problem: self signed certificate".
I am trying to disable SSL through /etc/apache2/sites-available/default-ssl.conf and restarting the apache service (i have also rebooted) but then i can't reach the non-https link of the application.

Steps to reproduce

  1. Precondition: I successfully reach https://example_ip/owncloud

open terminal
sudo nano /etc/apache2/sites-available/default-ssl.conf
set SSLEngine off
confirm changes and save the .conf

2.restart apache
sudo service apache2 restart

  1. I can't reach http://example_ip/owncloud

Expected behaviour

I thought that disabling the SSLEngine and restarting the apache service and/or rebooting i could open the non-https owncloud page

Actual behaviour

I cannot open neither the http or https page

Server configuration

Operating system: Raspbian Stretch kernel 4.0