Greetings,
We need some more info on this, is SSL certificate available on drop down list or do you receive any security warning while browsing your website over SSL/HTTPS??
you must have a custom domain linked to the Azure Website in order to configure an SSL BINDING and the domain for which the certificate is created for must match the custom domain.
Please refer below article for reference.
http://blogs.msdn.com/b/waws/archive/2014/12/01/my-ssl-certificate-doesn-t-work-on-azure-websites.aspx
Regards,
Somashekar
