can not get wp-cron to work after activate my site to use https

Hi all, my site was running well until i activated ssl on my site.
reconfigured http to https but since then my wp-cron does not work.
installed wp-crontrol plugin to check the events of wp-cron.

as i checked the cron events a massage appears on screen:
“There was a problem spawning a call to the WP-Cron system on your site. This means WP-Cron events on your site may not work. The problem was:
Failed to connect to mydomain.com port 443: Connection refused”

after some research – i did not find an entry which matches exactly my problem – i think the issue is the internal call to https://mydomain.com (443)….

Has anyone there an advice to solve my problem?

I am running wordpress on a vserver – ubuntu 14.4 – fcgi – ngix
My /etc/hosts contains:
127.0.0.1 mydomain.com mydomain localhost
::1 mydomain.com mydomain localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Thanks in advance

zocshe