What prompted the message? If you ran a line of code that just said reprex, this is what I would expect to see.
If you have the code you'd like to render as a reprex on your clipboard you need to either run library(reprex) beforehand and just run reprex() in the console, or run reprex::reprex() in the console with the namespace prefixed.
FYI, if you've installed library(tidyverse) you already have reprex installed. 