Sorry, i'll be more specific. It used to be next to the panels button on the top right.
Might you perhaps be referring to a Custom Toolbar Button that you created yourself? But checking the list of available hotkeys, there doesn't seem to be a sort hotkey.
Possibly he's talking about the "Tracks-->Sort By" menu option?? charlesbarkley, that's in the same place as 3.1.
Or it's this. But it can't be placed as a button.
What version were you using before, and what version are you using now?