I created a new Base account, created a new campaign, added a token and assigned it to myself, re-joined as player, and was able to use /fx fire on my token. If you intended it to work only in campaigns owned by Mentors, then that isn't working. If you intended it to be used only by GMs (as the Rugged Reroll release blog post implies), then that isn't working either. If it is meant to be usable by players, well that would need to be documented. =P The command does correctly give an error if you try to use it without a token selected, though. Using FX on a @target may not be implemented, but there's nothing leading a user to believe it should be implemented at this time.