Thanks for playing, and for letting me know!
Just to be sure, are you checking the tooltips from the item names / icons? The buy buttons do not have tooltips.
From my own testing it seems to work fine and I can't replicate the issue. If you don't mind, could you please provide more information so I can investigate? (which version you're playing, what platform/OS you're on, what you were doing/what happened before the tooltips stopped working, and how far into the game you were)