Hi,
@sslzen : i do not know, i have just installed 2 days, expired ssl certificate?
I have had uninstall and after that reinstall and active plugin. but it is same error:
SSL certificate cannot be installed!
Due to technical limitations, it’s currently not possible to install SSL certificate on an IP address or a localhost. Please install the plugin on a publicly facing, worldwide unique domain name such as sslzen.com and try again.