SSL, HTTPS not working – no padlock

Hello, I have installed Fastest Cache and SSL certificate. My website is directed automatically to https (beside of home page!) and it works, but I don’t have green padlock and there is Chrome’s note:

Your connection to XXXX is encrypted using an obsolete cipher suite. Further, this page includes other resources which are not secure. These resources can be viewed by others while in transit, and can be modified by an attacker to change the look of the page.

The connection uses TLS 1.2.

The connection is encrypted and authenticated using AES_128_GCM and uses DHE_RSA as the key exchange mechanism.

At the same time, wp-admin works great – there is green padlock and everything encrypted correctly, which clearly means it’s cache issue.

https://wordpress.org/plugins/wp-fastest-cache/