...
Progress window will open after clicking "Book" button.
Closing the window does not affect booking process. Everything happens in background, so you can close it. The view is further available on "Activity" page:
Product was successfully booked when "Account" and "External Order" fields appear, and they also moved to "Purchased" section:
You need to go to your personal account at Dropwow after booking where the order will be displayed:
...