Moving the topic to right place from beta
After billing , it looping to cart page back.
debug error message from chrome
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