Hi, the solution to this bug on windows is to change date+time settings to “Set time automatically” instead of manual. The trade tooltips will return and you will be able to trade as normal.
In this very specific case the problem seems to be not with the game files, but in the way the game interacts with your clock to enable the trade timer tooltip. So the usual suggested fixes such as disabling addons, deleting interface/wtf/cache folders, or even reinstalling the game will not work to solve it. Hope this helps.