Let me tell you the reason;
Chrome web browser says that your website is unsecure, it's not because there is a problem with your SSL certificate, it's because there are some links that starts with "http" instead of "https" in your web page. Because of this mixed content chrome gives an error like "Not trusted website", so when you update all links in your web page. The warning will disappear.
"What you look is me, what you see is you."
- Anonym
Senior Software Developer 
gmail.com