It looks like after a window is closed, the new window/widget in foreground doesn't receive a mouse enter/move notification. So we cannot press click directly, we've to move the mouse first.

Source

• step one, fix this bug Clicking dialog button after first time without moving mouse does nothing #1221
• don't ask two times for the same dropped file (done in 2240742)
• step two: related, add a "skip all" or "repeat for all files" option.