Hi Nurzan,
“One thing I did manually, outside the tutorial, was add a compositor bloom/glow effect.”
That may well be the cause of this. Not sure how exactly, but changing the Planet Material shouldnt have such a drastic efect on the Rings, so something else is causing it and if the Compositor is the only thing you did….
So, disable the Compositor and see if that gets the Rings back.
If it’s not that, you might need to post a link (via Dropbox, Googledrive, or so) to your .blend file, so we can troubleshoot.
