I am running Mathematica 11.2 on Windows.
Since some days I have the following problem: when I move the mouse curser over a command no pop up help is shown.
I found the following related question: in my case ShowCodeAssist is aeready set to True.
I also reinstalled Mathematica, without success.

$UserBaseDirectoryyet try that and restart mathematica – Coolwater Nov 28 '17 at 11:08