Mixed content issue

In my website only woocommerece checkout page is force secured checkout is on and have valid .
But there got an error ” Mixed Content: The page at ‘https://certifiedmedicalsales.com/checkout/’ was loaded over HTTPS, but requested an insecure XMLHttpRequest endpoint ‘https://certifiedmedicalsales.com/?wc-ajax=update_order_review’. This request has been blocked; the content must be served over HTTPS.”
And the “Your oprder and payment section not working the loader is on always.