Mixed scenario Internet with SSL and LAN

I have a Oc server running in my intranet with access from the internet with a StartSSL certifcate and a subdomain redirection.
As i want to speed up Lan upload i register clients computer trough the local ip address. The clients work fine, but when i try to login from the web interface, fails. The browser is redirected to the Internet address https://oc.domain.internet and i can´t log in as the login button can´t be used

I think it´s an issue because the SSL certicate.
Any ideas?

Thank you

If you have worries about you ssl setup, you can check it on ssllabs.com. StartSSL has also some security issues and most browsers won't accept certificates newer than Oct 2016. I'm not sure if other certificates are also kicked out at some point. That could be. Alternative: letsencrypt.com

Will check and let you know. Thank you