In other-words your HTML Source code have resources pointing to http, those requests are being blocked
To fix this all instances of HTTP in MySQL database must be replaced with HTTPS (http://www.example.com with https://www.example.com)
Is it risky?
In 99% of the cases its fine, but make sure to make backup of MySQL before proceeding.
You may need your MySQL database-name, username and password details but if you’re using wordpress PHP Script will automatically detect them
Download Search & Replace Script
Extract it & upload it to your domain’s document root, rename the folder as replace, which is easy to remember and easy to use.
If you are not using WordPress fill MySQL databasename, MySQL username & password
in replace field enter your http website address [Ex: http://www.guest.blog]
in with field enter your https website address [Ex: https://www.guest.blog]
Click Update Details & then click Live run, wait for the process to finish
When the script finishes click Delete Me button so your website will be safe.