Application Gateway WAF end to end SSL

We have enabled WAF and moved some of our web applications behind it. We have not faced any issues with HTTP sites but we are facing issues with end-to-end SSL. We initially faced an issue with the certificate on the backend server which has since been sorted out by MS Support. Our backend web server is running Apache with multiple HTTPS sites on the same server and the issue we face is regardless of the HTTPS site we try to access, only the url on top of Apache config is returned. Completely clueless on how to sort this out. Has anyone been able to implement end-to-end SSL with multiple HTTPS sites on the same Apache server?

Thanks.