Finally got the Media Viewer to work.
=> As it stood, for some reason I do not know, config.prod.yml was being ignored and therefore media viewer on the UI was not activated even when I set the media viewer to true in the config.prod.yml:
mediaViewer:
image: true
video: true
=> I had to modify the default-app-config.ts so as to set the media Viewer to true and after rebuilding the UI, voila, the media viewer displays and now works fine!
Glad I finally got it work after so many Months...….Still do not why config.prod.yml is being ignored in my production version of Dspace 7.6 (Kind of weird, since I setup a VM with Dspace 7.6 installed and the media viewer worked seamlessly after modification of config.prod.yml)
Hope this helps someone out there with a similar pain in the neck!