Must have gotten fixed because when I tried it earlier this morning it stated that option was not available or something like that. It does work now for me. I use uBlock Origin, Privacy Badger, Face book Container and WOT. The only problems I've had only involved WOT with Facebook...they do not like each other. Maybe we can get an Admin to clarify this report button thing?
I haven't noticed the Report button not working but I find that the Spam button comes up missing at times. It is not showing on any of the posts in this thread but I figure that is because you are all established members with a post count. It is irritating when it is on a spammer's post, though; I can still ban in other ways but it makes it less convenient.