DirectAdmin backend can't be accessed

At the backend SSL certificate, check the box to force jump to https, actually SSL certificate is not installed correctly, the backend can not be accessed, the browser prompts: use https
Can't access this website, check if there is a spelling error.
DNS_PROBE_FINISHED_NXDOMAIN.

In DirectAdmin's configuration file
Add "force_https=0" does not work and the site backend caot be accessed..

I very appreciate your help.
Nick