Fiori SES attachments not opening due to http link

The attachments in our SES app in Fiori are having http links unlike other apps where the link starts with https. Those http attachments are not opening (Gateway timeout error). But the same links open perfectly when the http is replaced by https. All of the above happens in QA. In Dev, the http attachments open correctly even though there is no difference in the SES app coding between QA and Dev. What could be wrong? What can we check in the web dispatcher? Are there some other things to be checked?