Not able to load config page

Hi,

I am finding difficulty in enabling the Secure Pages module. I have used this module before in other projects and it worked fine. But in my current project, once I enable it, I am not able to use Configure page. I even tried to copy paste direct link /admin/config/system/securepages, but it redirects me to page - /admin/config/system.
Also, after enabling the module, the admin pages doesn't load properly. The css and js files are not served using https, so the files are not fetched from server.
I have tried many configuration changes in .htacess and settings.php, but nothing has worked yet.
Pelase help.