You could try searching the forum where such questions have been asked many times in the past:
!howlong has suddenly stop working!
!followage command is no longer working
Here is one command that will do what you need and you can copy paste into chat:
!commands add !followsince $(urlfetch https://2g.be/twitch/following.php?user=$(touser)&channel=$(channel)&format=mwdhms)