4.2 OnePage Checkout error

Moving the topic to right place from beta

After billing , it looping to cart page back.
debug error message from chrome
Jquery-3.3.1.min.js

Mixed Content the page at 'https://www.nop.com/onepagecheckout' was loaded over HTTPS, but requested jquery.3.3.1min.js an insecure XMLHttpRequest endpoint
'http://www.nop.com/checkout/OpcsaveBilling'. The request has been blocked; the content must be served over HTTPS

Hello,

Verify once this setting at general setting.

It should be true.if false than set it true and restart your store.

Force SSL for all site pages

Yes. it is already true; but OPCbilling page does use SSL / https;
I have used my ssl server setting from flexibile to Force HTTPS. its all good now