I recently purchased the rtMedia Moderation addon and installed and activated it, however the report button does not show up anywhere on the activity or media uploads.
It should work. Please check the moderation is ON under rtMedia -> Settings -> Moderation. Refer the settings document here http://docs.rtcamp.com/rtmedia/addons/moderation.html.
If problem still persist, please create a premium support ticket https://rtcamp.com/premium-support/ and provide login details of your site.