The ring works just fine already - it's always worked properly in my play-throughs at least. What it doesn't do is tell you anything at all about what it's doing - there's no indication that it's working unless you know what to look for.
What I found was that when my halfling character (no darkvision) was wearing the ring, she would never have disadvantage to attack her targets, despite a lack of light. When removing it, the disadvantage would return. Characters with darkvision didn't appear to gain any benefit. It doesn't visibly grant you darkvision, but it seems to have the effect of doing so in terms of targeting enemies, currently.