Hey Houmam - so a couple of things here. The first is you MUST have allow_url_fopen = ON for UNA. Not sure who you have hosting with but, you may have to reach out to them and have them turn this on for you if you do not have the ability yourself. 

The second is whether you have your cron jobs setup properly since this is used to "execute" the updates. If you go into Studio > Dashboard > Hosting Tools > then Server Audit, scroll down to Site Setup and in the Cron Jobs area, do you see the command for your cron job there and does it have a "Last cron jobs execution". Your cron job command would look something like (may not look exactly like this):

MAILTO=""

SHELL="/usr/bin/bash"

* * * * * /opt/plesk/php/7.1/bin/php -q /var/www/vhosts/mywebsite.com/httpdocs/periodic/cron.php